JP2004123510A - Apparatus for manufacturing single crystal and method for manufacturing the same - Google Patents

Apparatus for manufacturing single crystal and method for manufacturing the same Download PDF

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Publication number
JP2004123510A
JP2004123510A JP2003150713A JP2003150713A JP2004123510A JP 2004123510 A JP2004123510 A JP 2004123510A JP 2003150713 A JP2003150713 A JP 2003150713A JP 2003150713 A JP2003150713 A JP 2003150713A JP 2004123510 A JP2004123510 A JP 2004123510A
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single crystal
crucible
crystal
heat
radiant heat
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JP4203647B2 (en
Inventor
Shigeki Hirasawa
平澤　茂樹
Masato Ikegawa
池川　正人
Hiroyuki Ishibashi
石橋　浩之
Akihiro Gunji
軍司　章弘
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Hitachi Ltd
Resonac Corp
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Hitachi Chemical Co Ltd
Hitachi Ltd
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/14—Heating of the melt or the crystallised materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1032—Seed pulling
    • Y10T117/1068—Seed pulling including heating or cooling details [e.g., shield configuration]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1032—Seed pulling
    • Y10T117/1072—Seed pulling including details of means providing product movement [e.g., shaft guides, servo means]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1076—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone
    • Y10T117/1088—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone including heating or cooling details

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for manufacturing a single crystal capable of lowering a fraction defective in manufacturing the single crystal. <P>SOLUTION: The apparatus for manufacturing the single crystal is provided with a crucible 1 for housing a raw material, a heating means 11 for heating the raw materials in the crucible 1 and a crystal moving means 17 for upwardly moving a seed crystal 13 from the interior of the crucible 1. The apparatus consists of the configuration provided with a heat-transfer member 3 which extends upward from the vicinity of the upper end portion of at least the side wall of the crucible 1, encloses the formed single crystal 15 and is formed of a material having heat conductivity, and a boundary portion radiation heat shielding body 7 which shields the upward radiation heat from the boundary portion between a tapered part 15a of the gradually expanding diameter continuous with the seed crystal 13 of the formed single crystal 15 and a cylindrical straight trunk part 15b continuous with the tapered part 15a of the formed single crystal 15 at least in cooling after the growth of the single crystal. As a result, the temperature differences in the radial direction of the single crystal 15 can be decreased, the occurrence of of defects and cracks can be reduced and the fraction defective in manufacturing of the single crystal can be lowered. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば電子機器や医療用機器などに用いられる単結晶の製造技術に関する。
【０００２】
【従来の技術】
加熱にした原料の融液に種結晶を接触させ、この種結晶を引き上げることで、単結晶を製造する単結晶の製造技術が知られている。単結晶の育成は、通常、次の手順で行われる。炉本体内部に、単結晶の原料をいれるとともに周囲に加熱手段を備えたルツボを配置し、前記加熱手段でルツボを加熱して高温になったルツボで原料の融液を加熱する。この融液の表面に、製造しようとする単結晶よりも径の小さい種結晶を接触させると、種結晶と接触した融液は種結晶を介して放熱して冷却され、種結晶の結晶の方向に揃うように結晶を成長させる。結晶の成長に合わせて種結晶が引き上げられ、成長した結晶が順次冷却されてさらに結晶が成長する。これが繰り返されて単結晶が生成される。単結晶成長の初期の段階では、結晶の径を大きくするため、種結晶を引き上げつつ、種結晶から円錐形に径が大きくなるテーパ部を形成する。種結晶の径が所定の大きさに達したら、径を漸次拡大するテーパ部の形成は止められ、軸方向に円柱状に結晶が成長するの直胴部の形成が始まる。
【０００３】
このとき、融液の液面はルツボの上端から下がった位置にあるため、引き上げられる単結晶は、ルツボ上端よりも下にある間はルツボ内周面からの放射熱を受けて加熱され、ルツボ上端よりも上に出た部分は、熱を放出して冷却される。十分な長さの直胴部を形成した後、直胴部を融液から離し、ルツボの加熱量を徐々に減らして室温まで冷却する。
【０００４】
このような単結晶の製造技術において、欠陥や割れなどが発生すると、欠陥や割れなどが発生した部分は、不良箇所となり製品にならない。したがって、不良箇所の発生率、つまり不良率を低減することが生産性を向上するために必要とされている。単結晶における欠陥や割れなどの発生の原因の一つは、単結晶の育成時や、形成した単結晶の冷却時における単結晶内の温度分布にある。
【０００５】
このような単結晶の育成時や単結晶の冷却時における単結晶内の長手方向の温度分布つまり温度勾配を適正にするための単結晶の製造技術として、単結晶の上方に放射熱反射板を配置して単結晶の上方への熱放散を抑制し、単結晶の引き上げと共に放射熱反射板を上昇させることが提案されている（例えば、特許文献１参照）。さらに、単結晶が生成されるルツボを収容した炉本体の上部開口に、可動式の耐火蓋を設けることが提案されている（例えば、特許文献２参照）。また、単結晶が生成されるルツボの上部に蓋を設けることが提案されている（例えば、特許文献３参照）。
【０００６】
一方、ルツボ内の融液の温度勾配により生じる密度勾配に起因する自然対流や、表面張力勾配に起因するマランゴリ対流などがルツボ内の融液で発生している。これらの融液の対流が発生すると、単結晶が育成されている部分、つまり単結晶の固液界面部分が平坦にならず、例えば凹状や凸状となり、これにより、単結晶の固液界面近傍部分における半径方向の温度分布が不均一となる。このような、単結晶の固液界面近傍部分における温度分布の不均一を低減する単結晶の製造技術として、単結晶の固液界面部分の形状をできるだけ平坦にするため、単結晶を引き上げる際に、単結晶を回転させたり、円筒状のルツボの中心軸を回転軸として回転させることで、ルツボの半径方向に広がる融液の強制対流を生起させ、融液の全体の対流パターンを制御することが提案されている（例えば、特許文献４参照）。
【０００７】
【特許文献１】
特開平８−１７５８９６号公報（第３−４頁、第５図）
【特許文献２】
特開平６−１５７１８７号公報（第２頁、第１図）
【特許文献３】
特開２００１−３１６１９５号公報（第４−６頁、第１図、第３図）
【特許文献４】
特開平６−１８３８７７号公報（第３−４頁、第１図）
【０００８】
【発明が解決しようとする課題】
特許文献１は、単結晶育成過程において単結晶内の長手方向の温度分布を低減して欠陥や割れなどの発生を低減しようとするものである。しかし、単結晶の直上位置に放射熱反射体を設けると冷却時に単結晶内の半径方向における温度分布の差が増大してしまうため、欠陥や割れなどの発生を低減し難い。特許文献２は、冷却過程において耐火物上部に蓋をすることにより冷却速度を遅くし、単結晶内の温度分布を低減して欠陥や割れなどの発生を低減しようとするものである。しかし、単結晶の育成過程における単結晶の表面温度の制御に関して考慮がなされておらず、単結晶の育成過程における温度分布を適正にすることはできず、やはり、欠陥や割れの発生を低減し難い。
【０００９】
特許文献３は、ルツボの上部に蓋を設けているため、冷却過程でのルツボ上方における単結晶の表面温度を制御することはできず、やはり、単結晶の育成過程における温度分布を適正にすることはできず、欠陥や割れの発生を低減し難い。加えて、単結晶の育成過程の初期においても、ルツボ上部に蓋が設けられているため、単結晶のテーパ部の面、つまりテーパ面が温度上昇して表面粗れが生じ、逆に欠陥や割れなどが発生し易くなる場合がある。このように、特許文献１乃至３の単結晶の製造技術では、欠陥や割れなどの発生を低減できない場合があり、不良率を低減することは難しい。
【００１０】
一方、加熱手段として高周波コイルを含む高周波発生手段を用いた高周波誘導加熱では、単位時間に対する単位体積当たりの発熱量は、金属の表面に誘起される周方向の電流ＪΘの２乗に比例する。そして、コイルに近い金属ほどＪΘは大きくなる。また、電磁界は、金属の角部の表面に集中する性質がある。そこで、高周波誘導加熱により、円筒形のルツボを加熱すると、ルツボの側壁の上端部分と下端部分となる底の周縁部分とに電磁界が集中する。このため、これらのルツボの側壁の上端部分と下端部分での発熱量が他の部分よりも大きくなる。このため、例えば側壁が底の径よりも軸方向に長くなるに連れて、側壁のルツボ側壁の上端部分と下端部分以外の部分の温度が上端部分と下端部分の温度に比べて低くなって行く。したがって、ルツボの温度分布が不均一になり、特許文献４のように、種結晶やルツボを回転させても、融液は、望ましくない対流パターンを呈し、単結晶の固液界面部分が平坦にならない場合がある。
【００１１】
さらに、特許文献４のように単結晶やルツボが回転することで、半径方向に広がる強制対流を生起させて、単結晶の固液界面部分を平坦にできる場合であっても、種結晶からテーパ部を育成する過程では、単結晶の直胴部が育成されているときに比べて結晶の外径が小さいため、半径方向に広がる強制対流を十分に生起させることができない。このため、ルツボの底の大きさなどの条件によって、種結晶からのテーパ部の育成段階で、ルツボ内の融液は、望ましくない対流パターンを呈し、単結晶の固液界面部分が平坦にならない場合がある。このように、特許文献４の単結晶の製造技術でも、ルツボの大きさや形状などの条件によって、単結晶の固液界面部分が平坦にならず、温度分布が不均一となるため、欠陥や割れなどの発生を低減できない場合があり、不良率を低減することは難しい。
【００１２】
本発明の課題は、単結晶の製造における不良率を低減することにある。
【００１３】
【課題を解決するための手段】
結晶に生ずる欠陥や割れなどの発生の主な原因の一つは、冷却過程において単結晶の中心部よりも外周部が先に冷却されるため、単結晶内の温度分布が不均一になることにある。特に、単結晶の半径方向の温度差による熱応力の影響が大きいのに比較して、単結晶の長手方向の直線的な温度分布による熱応力は小さいことを本発明の発明者らは見いだした。このことから、冷却過程において結晶の外周面を保温することにより単結晶の半径方向における温度差を低減することが有効であること、さらに、単結晶の半径方向における温度差を低減すると共に、単結晶の上端面つまりテーパ部のテーパ面のみを冷却して長手方向における温度分布を直線的にして冷却速度を維持することが有効であることを本発明の発明者らは見いだした。
【００１４】
そこで、本発明の単結晶の製造装置は、原料を収容するルツボと、該ルツボ内の原料を加熱する加熱手段と、種結晶を前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、少なくとも前記ルツボの側壁の上端部分近傍から上方に延在し、形成される単結晶を囲み、伝熱性を有する材料で形成した伝熱部材を設けた構成とすることにより上記課題を解決する。
【００１５】
このような構成とすることにより、ルツボから出た単結晶が冷却されるとき、単結晶の下方にあるルツボの熱が伝熱部材によってルツボ外の上方に伝わり、単結晶の外周面からの放熱量を低減する。このため、単結晶の半径方向における温度差が低減される。したがって、欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００１６】
また、本発明の単結晶の製造装置は、少なくとも単結晶育成後の冷却時に、形成された単結晶の種結晶に連続して漸次拡径するテーパ部と形成された単結晶のテーパ部に連続する円柱状の直胴部との境界部分から上方への放射熱を遮断する境界部分放射熱遮断体を設けた構成とすることにより上記課題を解決する。
【００１７】
このようにすれば、ルツボから出た単結晶の直胴部が冷却されるとき、単結晶の直胴部外周面から上方への放射伝熱による放熱が遮断されると共に、装置上方から比較的低温のガスが単結晶の直胴部外周面の周囲に流入することが遮断される。このため、単結晶の直胴部内の半径方向における温度差が低減される。さらに、単結晶のテーパ部のテーパ面のみを冷却して長手方向における温度分布を直線的にして冷却速度を維持できる。したがって、欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００１８】
さらに、テーパ部と直胴部との境界部分から上方への放射熱を遮断する放射熱遮断体が上下方向に移動可能であり、この放射熱遮断体を上下方向に移動させる境界部分放射熱遮断体移動手段を設けた構成とする。このような構成とすれば、単結晶の育成時にも放射熱遮断体をテーパ部と直胴部との境界部分に位置させ、テーパ部と直胴部との境界部分から上方への放射熱などを遮断できるため、欠陥や割れなどの発生をより低減でき、不良率をより低減できる。
【００１９】
また、結晶に生ずる欠陥や割れなどの発生の別の原因は、単結晶の育成時にテーパ部のテーパ面の温度が上昇し過ぎ表面粗れが生じることにあることを本発明の発明者らは見いだした。単結晶の成長初期の、単結晶のテーパ部がルツボ内に位置しているテーパ部の形成時において、テーパ部のテーパ面の温度上昇を抑制することが、このテーパ面の表面粗れを抑制するのに有効である。一方、単結晶のテーパ部が形成された後の、単結晶の直胴部の形成時には、ルツボから出ているテーパ部からの放熱を大きくし、かつルツボ内にある直胴部の外周面からの放熱を低減することが、融液の液面位置、つまり固液界面位置における、生成中の単結晶の半径方向における温度分布の不均一、つまり温度差を低減するのに効果がある。
【００２０】
そこで、本発明の単結晶の製造方法は、原料を入れたルツボを加熱し、原料の融液に種結晶を接触させながら引き上げて単結晶を製造する単結晶の製造方法であって、単結晶の直径を大きくする単結晶の成長初期の単結晶のテーパ部形成時及びテーパ部に連続して円柱状に成長する単結晶の直胴部形成時のうち、単結晶のテーパ部形成時には、ルツボの内面から単結晶のテーパ部に到達するの放射熱を遮断することにより上記課題を解決する。
【００２１】
また、本発明の単結晶の製造装置は、単結晶を囲み、ルツボの内面からこのルツボの内に位置する単結晶に向かう放射熱を遮断するルツボ内放射熱遮断体と、この放射熱遮断体を上下方向に移動させるルツボ内放射熱遮断体移動手段とを設け、このルツボ内放射熱遮断体移動手段は、単結晶成長初期の単結晶の直径を大きくする単結晶のテーパ部形成時に、単結晶のテーパ部を囲む位置にルツボ内放射熱遮断体を移動させ、テーパ部に連続して円柱状に成長する単結晶の直胴部形成時には、単結晶から離れた位置にルツボ内放射熱遮断体を移動させる構成とすることにより上記課題を解決する。
【００２２】
このような構成とすれば、単結晶のテーパ部の形成時には、ルツボ内面からの放射熱によるテーパ部のテーパ面の加熱がルツボ内放射熱遮断体により抑制され、テーパ面の温度上昇が抑制され、テーパ面の表面粗れを抑制できる。一方、単結晶の直胴部の形成時には、ルツボ内放射熱遮断体が結晶から離れた位置に移動するため、単結晶のテーパ部から上方への放熱が妨げられず、ルツボ内に位置する単結晶の直胴部の外周面がルツボ内面からの放射熱を受けることにより、単結晶の直胴部の外周部の温度降下が低減され、結晶成長面、つまり融液の液面位置における単結晶の半径方向における温度差を低減できる。したがって、欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００２３】
さらに、加熱手段が軸線を上下方向にしてルツボを囲んで巻回され高周波電流が通電される高周波コイルを含む高周波発生手段であり、単結晶を囲み、ルツボの内面からこのルツボの内に位置する単結晶に向かう放射熱を遮断するルツボ内放射熱遮断体は、非金属性の材料で作り、中央に種結晶、及び結晶移動手段の棒状または帯状のシードホルダーを挿通可能な開口を備えた円錐形状、もしくは内径が単結晶の直胴部の径より大きい円筒形状とした構成とすることが望ましい。
【００２４】
さらに、本発明の単結晶の製造方法は、単結晶の直径を大きくする単結晶の成長初期の単結晶のテーパ部形成時及びテーパ部に連続して円柱状に成長する単結晶の直胴部形成時のうち、単結晶の直胴部形成時には、ルツボの上端部分から上方への放射熱を遮断することにより上記課題を解決する。
【００２５】
また、本発明の単結晶の製造装置は、単結晶が挿通可能でルツボの上端部分から上方への放射熱を遮断する直胴部放射熱遮断体と、この直胴部放射熱遮断体を上下方向に移動させる直胴部放射熱遮断体移動手段とを設け、加熱手段は、ルツボの上端部分よりも下側の部分を加熱し、直胴部放射熱遮断体移動手段は、単結晶成長初期の、単結晶の直径を大きくする単結晶のテーパ部形成時には、直胴部放射熱遮断体をルツボの上端部分から離れた位置に移動させ、テーパ部に連続して円柱状に成長する単結晶の直胴部形成時には、直胴部放射熱遮断体を、単結晶の直胴部外周面とルツボの内周面との間、もしくは単結晶の直胴部外周面とルツボの上端部分との間に位置させる構成とすることにより上記課題を解決する。
【００２６】
このようにすれば、単結晶の直胴部の形成時には、直胴部放熱遮断体により、ルツボ内にある単結晶の直胴部の外周面からの放熱が低減されるので、単結晶の生成面、すなわち、融液の液面位置における単結晶の半径方向における温度差を低減できる。一方、単結晶のテーパ部の形成時には、テーパ部のテーパ面からの放熱を妨げるものがないので、テーパ部から上方へ放熱ができ、ルツボの融液液面よりも上の部分の加熱量を少なくすることにより、テーパ面の温度上昇を抑制し、表面粗れを抑制できる。したがって、欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００２７】
さらに、加熱手段が軸線を上下方向にしてルツボを囲んで巻回され高周波電流が通電される高周波コイルを含む高周波発生手段であり、単結晶が挿通可能でルツボの上端部分から上方への放射熱を遮断する放射熱遮断体が金属製である構成とすれば、単結晶の直胴部外周からの放熱を更に少なくし、単結晶の生成面、すなわち、融液の液面位置における単結晶の半径方向における温度差をより低減できる。
【００２８】
また、本発明の単結晶の製造装置は、原料を収容するルツボと、このルツボを囲んで設けられた高周波コイルを含む高周波発生手段と、種結晶を回転させながら前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、ルツボの側壁の上端部分と下端部分との間の部分を、高周波発生手段の作動により加熱する壁側加熱部材を設けた構成とすることにより上記課題を解決する。
【００２９】
このような構成とすれば、壁側加熱部材を設けている場合、ルツボの上端部分や下端部分に加えて、ルツボの上端部分と下端部分との間の部分も加熱するようになり、ルツボの側壁の温度分布を均一化できる。この結果、ルツボの側壁に沿って液面に向かって上昇する融液の対流を生起させることができ、ルツボ内の融液が望ましくない対流パターンを呈するのを防ぐことができる。したがって、ルツボの大きさや形状などの条件に関係なく単結晶の固液界面部分を平坦化して欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００３０】
さらに、本発明の単結晶の製造装置は、ルツボの底に、この底の中央部分を、高周波発生手段の作動により加熱する底側加熱部材を設けた構成とすることにより上記課題を解決する。
【００３１】
このような構成とすれば、底側加熱部材を設けている場合、ルツボの下端部分、つまりルツボの底の周縁部分に加えて、底の中央部分を加熱するようになり、ルツボの底の中央部分から種結晶または単結晶の固液界面部分に向かって上昇し、種結晶または単結晶の固液界面部分に当たって半径方向に広がる融液の対流を生起させることができ、ルツボ内の融液が望ましくない対流パターンを呈するのを防ぐことができる。したがって、ルツボの大きさや形状などの条件に関係なく単結晶の固液界面部分を平坦化して欠陥や割れなどの発生を低減でき、不良率を低減できる。
【００３２】
また、壁側加熱部材は、ルツボの側壁外面の上端部分と下端部分との間の部分に、導電性を有する材料でルツボの側壁外面の周方向に沿って延在させて設けた突起状の部材で形成されている構成とする。このような構成とすれば、高周波コイルで発生した電磁界は、高周波コイルに近く尖った角部に集中するため、高周波コイルで発生した電磁界によって、ルツボの上端部分や下端部分に加えて、突起状の部材で形成された壁側加熱部材も発熱し、ルツボの上端部分と下端部分との間の部分を加熱できる。
【００３３】
さらに、底側加熱部材は、ルツボの底外面の中央部分に熱を伝える熱伝導性を有する材料で形成した伝熱部と、この伝熱部よりも大きな径を有し、導電性を有する材料で形成した盤状の発熱部とで形成されている構成とする。また、加熱部材は、ルツボの底外面の中央部分に対応する位置に伝熱部となる貫通穴を有する断熱性の材料で形成した断熱部材と、この断熱部材の貫通穴よりも大きな径を有し、導電性を有する材料で形成した盤状の発熱部とで形成されている構成とする。このような構成とすれば、高周波コイルで発生した電磁界は、高周波コイルに近く尖った角部に集中するため、高周波コイルで発生した電磁界によって、底側加熱部材の発熱部の周縁部でも発熱する。この発熱部の熱が底側加熱部材の伝熱部または断熱部材の貫通穴を介してルツボの底の中央部分に伝えられるため、ルツボの底の中央部分を加熱できる。
【００３４】
さらに、発熱部が円盤状であり、発熱部の直径がルツボの底の直径の２／３以上である構成とすれば、高周波発生手段により確実に発熱部の周縁部分で発熱させることができる。
【００３５】
また、壁側加熱部材及び底側加熱部材がルツボに着脱自在に取り付けられている構成とする。さらに、壁側加熱部及び底側加熱部がルツボと接触した位置と、壁側加熱部材及び底側加熱部材がルツボと離れた位置との間で壁側加熱部材及び底側加熱部材を移動する加熱部材移動手段を設けた構成とする。このような構成とすれば、単結晶を育成する段階などに応じて、壁側加熱部材及び底側加熱部材をルツボに着脱し、ルツボの側壁及び底の壁側加熱部及び底側加熱部による加熱を必要に応じて選択できる。
【００３６】
また、高周波コイルを含む高周波発生手段と、種結晶を回転させながら前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置を用いて単結晶を育成するとき、ルツボの側壁の上端部分と下端部分との間の部分及びルツボの底の中央部分の少なくとも一方を加熱する単結晶の育成方法とすれば、ルツボ内の融液の加熱分布を制御できるため、育成する単結晶の品質を向上できる。
【００３７】
上記のいずれかに記載の単結晶の製造装置あるいは単結晶の製造方法により製造した単結晶とすれば、単結晶の品質を向上できる。
【００３８】
【発明の実施の形態】
（第１の実施形態）
以下、本発明を適用してなる単結晶製造技術の第１の実施形態について図１及び図２を参照して説明する。図１は、本発明を適用してなる単結晶の製造装置の概略構成を冷却過程の状態で示す縦断面図である。図２は、本発明を適用してなる単結晶の製造装置の概略構成を育成過程の状態で示す縦断面図である。
【００３９】
本実施形態の単結晶の製造装置は、例えば融点が１５００℃以上といった単結晶の製造装置であり、図１及び図２に示すように、円筒状のルツボ１、ルツボ１の側壁１ａ外面を囲み、ルツボ１よりも高さが高い円筒状の伝熱部材３、伝熱部材３の上端部分に設けられて中央部分に開口５を有する円盤状の境界部分放射熱遮断体となる放射熱遮断部材７、伝熱部材３の外側を取り囲む耐火物９、耐火物９の外側で高周波を発生する高周波コイル１１を含む高周波発生手段、そして種結晶１３及び育成された単結晶１５を保持する棒状または帯状のシードホルダー１７を含んでシードホルダー１７に保持された結晶を回転させながら上方に引き上げる結晶移動手段などを備えている。
【００４０】
ルツボ１は、上端が開口され、下端が閉塞されて底１ｂが形成された円筒状の容器であり、導電性を有し高融点の金属材料、例えばイリジウム、白金、タングステン、モリブデンなどで形成されている。伝熱部材３は、伝熱性を有する材料、例えば高熱伝導アルミナ、セラミック、イリジウムなどで形成されている。伝熱部材３は、上端と下端が開口されて、内径が、ルツボ１の外径と同じか、または、ルツボ１の外径より大きい円筒状であり、ルツボ１及びルツボ１の上方の空間を囲んだ状態で設置されている。伝熱部材３の上端は、図１に示すような単結晶の製造の冷却過程において単結晶１５が保持されているときに、単結晶１５の漸次拡径する円錐状のテーパ部１５ａと、テーパ部１５ａに連続して形成される円柱状の直胴部１５ｂとの境界部分に対応する位置に在る。
【００４１】
境界部分放射熱遮断体となる放射熱遮断部材７は、中央部分に単結晶１５の直胴部１５ｂの径よりも大きな径を有する開口が形成された円盤状または平板リング状で、放射熱を遮断可能な材料、例えばイリジウム、アルミナ、セラミック、ジリコニアなどで形成されている。放射熱遮断部材７は、伝熱部材３の上端に対応する位置、つまり単結晶の製造の冷却過程において保持された単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分に対応する位置に、耐火物９に外周縁部分が取り付けられて保持されている。放射熱遮断部材７の中央部分に設けられた開口は、単結晶１５に接触しないできるだけ小さいな径で形成することが望ましい。また、放射熱遮断部材７を形成する材料は、放射熱を遮断可能であれば、伝熱性を有する材料であっても、断熱性の材料であってもよいが、放射熱の遮断能力を向上する上では断熱性の材料を用いる方が望ましい。
【００４２】
耐火物９は、上端が開口され、下端が閉塞されて底が形成されたルツボ１及び伝熱部材３よりも大きな円筒状の容器であり、絶縁性と断熱性を有する高温耐性の材料、例えば低熱伝導アルミナ、ジリコニア、アルミナウールなどで形成されている。耐火物９の高さは、伝熱部材３よりも高くなっている。高周波発生手段は、図１及び図２では図示していない高周波電源や、高周波電源と図示していない配線で電気的に接続された高周波コイル１１などを備えている。高周波コイル１１は、耐火物９の外側で、ルツボ１の側壁１ａに対応する位置に、上下方向を中心軸として、この耐火物９の外側を取り囲んだ状態で設置されている。結晶移動手段は、棒状または帯状のシードホルダー１７、そしてシードホルダー１７が垂下されると共に、シードホルダー１７を回転させながら引き上げる図示していない駆動部などを備えている。
【００４３】
なお、ルツボ１、伝熱部材３、放射熱遮断部材７、耐火物９、高周波コイル１１、そして、シードホルダー１７の一部分などは、容器１９内に収容されている。ルツボ１は、容器１９の底面に設置された支持部材２１上に支持されている。また、容器１９の天井には、ルツボ１の開口の中央部分に対応する位置に貫通穴２３が形成されており、この貫通穴２３にシードホルダー１７が上方から垂下された状態で挿通されている。
【００４４】
このような構成の単結晶の製造装置の動作と本発明の特徴部について説明する。ルツボ１中には、結晶の原料である結晶材料、例えばＧｄ２ＳｉＯ５、Ｂｉ４Ｇｅ３Ｏ１２、Ｌｕ２ＳｉＯ５などが収容されており融液２５となっている。図示していない高周波電源から高周波電流を高周波コイル１１に流すと、導電性のルツボ１に誘導電流が流れる。これにより、ジュール加熱によってルツボ１が加熱され、昇温したルツボ１内の融液２５が加熱された状態となる。この状態で、この融液２５に、シードホルダー１７の下端部に保持された種結晶１３を接触させて、融液２５から引き上げると、図２に示すように、単結晶１５が生成される。単結晶の製造は、図２に示すように、最初、種結晶１３に連続して漸次拡径する円錐状に単結晶１５のテーパ部１５ａを形成し、テーパ部１５ａに連続して、円柱状の直胴部１５ｂを形成する育成過程と、図１に示すように、生成された単結晶１５を引き上げた状態でシードホルダー１７に保持したまま放置して冷却する冷却過程とを含んでいる。
【００４５】
図２に示すような育成過程では、育成される単結晶１５は、種結晶１３及び単結晶１５の表面から放射伝熱によって容器１９の天井に向かって放熱され、さらに、種結晶１３とシードホルダー１７を経た熱伝導によって冷却されることにより、結晶材料の融点以下となっているため、融液２５に接触している単結晶１５の下面が成長面１５ｃとなり、新しい結晶が成長する。
【００４６】
このとき、ルツボ１の発熱は、融液２５に接している部分と、融液２５より上方にある部分との両方で生じるが、このルツボ１の発熱により生じた熱は、伝熱部材３を伝導し、ルツボ１よりも上方に伝わる。このため、伝熱部材３によって囲まれた空間は、伝熱部材３が内場合に比べ、どの高さにおいても生成直後の単結晶１５に近い温度になっている。したがって、育成過程においてルツボ１から上方に出て冷却される単結晶１５の外周面からルツボ１外の単結晶１５の周囲の空間への放射伝熱による放熱が少なくなり、単結晶１５の半径方向の温度差が低減される。
【００４７】
一方、冷却過程は、図１に示すように、長く成長した単結晶１５を融液２５から離し、加熱量を少しづつ減らして室温まで冷却するものである。この冷却過程においては、十分に長く成長した単結晶１５を上方に移動し、融液２５から切り離す。高周波コイル１１から発生する高周波電力を少しづつ低減することにより、温度を下げてゆく。このとき、育成過程と同様に、伝熱部材３にルツボ１の発熱による熱が伝わることにより、単結晶１５の外周面からルツボ１外の単結晶１５の周囲の空間への放熱が少なくなる。
【００４８】
さらに、冷却過程では、単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分に対応する位置に放射熱遮断体７が在るため、放射熱遮断体７が蓋の役割を果たし、単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分から上方への放射伝熱による放熱が少なくなる。容器１９内の天井部分などの比較的低温のガスが単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分から下方に流入し難くなる。つまり、単結晶１５の直胴部１５ｂのみが保温され、単結晶１５の直胴部１５ｂのみからの放熱が低減された状態となる。これにより、単結晶１５の直胴部１５ｂの半径方向における温度差が低減される。
【００４９】
一般的に、冷却過程では、育成過程と異なり、ルツボ１の発熱が小さいため単結晶１５の半径方向における温度差、つまり不均一な温度分布が生じやすい。しかし、本実施形態では、伝熱部材３と放射熱遮断体７の両者の作用が合わさって冷却過程での単結晶１５の直胴部１５ｂ外周面からの放熱が少なくなり、半径方向の温度差が低減される。さらに、単結晶１５のテーパ部１５ａでは、テーパ部１５ａのテーパ面からの放射伝熱と、容器１９内の比較的低温のガスがテーパ部１５ａのテーパ面に流ることによる対流伝熱とによる放熱があり、適切な冷却速度で単結晶１５を冷却できる。テーパ部１５ａのテーパ面からの放熱により単結晶１５の縦方向、つまり長手方向には温度勾配が一定の直線的温度分布を有して生じるが、この長手方向の温度勾配つまり温度差による熱応力は小さいため、この長手方向の温度差により欠陥や割れなどは生じ難い。
【００５０】
このように、本実施形態の単結晶の製造装置及び単結晶の製造方法では、伝熱部材３を備えており、ルツボ１から出た単結晶１５が冷却されるとき、ルツボ１の熱が伝熱部材３によってルツボ１外の上方の伝熱部材３で囲まれた空間に伝わり、単結晶１５の外周面からの放熱量を低減する。このため、単結晶１５の半径方向における温度差が低減される。したがって、欠陥や割れなどの発生を低減でき、単結晶の製造における不良率を低減できる。
【００５１】
さらに、本実施形態の単結晶の製造装置及び単結晶の製造方法では、単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分から上方への放射熱を遮断する放射熱遮断体７を備えているため、冷却過程において単結晶１５が冷却されるとき、単結晶１５の直胴部１５ｂ外周面からの放射伝熱による放熱が遮断されると共に、容器１９内の天井近傍などから比較的低温のガスが単結晶１５の直胴部１５ｂ外周面の周囲の空間に流入することが遮断される。このため、単結晶１５の直胴部１５ｂ内の半径方向における温度差が低減される。また、単結晶１５のテーパ部１５ａのテーパ面のみを冷却して単結晶１５の長手方向における温度分布を直線的にして冷却速度を維持できる。したがって、欠陥や割れなどの発生を低減でき、単結晶の製造における不良率を低減できる。
【００５２】
加えて、本実施形態の単結晶の製造装置及び単結晶の製造方法では、放射熱遮断体７と共に伝熱部材３を備えているため、冷却過程において単結晶１５の直胴部１５ｂの保温効果を向上でき、欠陥や割れなどの発生をより低減し、単結晶の製造における不良率をより低減できる。
【００５３】
さらに、欠陥や割れなどの発生をより低減できるということは、欠陥や割れに繋がる結晶の欠落を低減できることであり、製品となった単結晶の結晶の欠落も低減できることとなるため、製品化された単結晶の品質を向上することもできる。
【００５４】
ところで、従来の単結晶の製造技術では、単結晶の直上位置に放射熱反射体を設けたり、冷却過程にて耐火物上部に蓋をしたり、ルツボ上部に蓋を設けている。このため、育成過程や冷却過程における冷却時間が長くなり、育成過程における単結晶の成長速度が低下すると共に、冷却過程における単結晶の冷却時間が長くなることから、生産能力が低下してしまうという問題もある。
【００５５】
これに対して、本実施形態の単結晶の製造技術では、育成過程では、蓋となるものが無い状態であり、冷却過程では、単結晶のテーパ部から放熱できる状態であるため、育成過程における単結晶の成長速度が低下し難く、また、冷却過程における冷却時間は長くなり難い。したがって、生産能力の低下を抑制することができる。
【００５６】
また、本実施形態では、境界部分放射熱遮断体として、伝熱部材３の上端部分に設けられて中央部分に開口５を有する円盤状の放射熱遮断部材７を示したが、境界部分放射熱遮断体は、このような構成に限らず、単結晶の直胴部とテーパ部との境界部分に対応する位置に在り、上方への放射熱を遮断できれば様々な構成にすることができる。例えば、図３に示すように、耐火物９の上端部を冷却過程における単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分に対応する位置とし、この耐火物９の上端部に、この上端部から単結晶に向かってリング状に突出した蓋部９ａを境界部分放射熱遮断体として形成した構成とすることもできる。
【００５７】
このとき、耐火物９は、厚みがあるため、耐火物９の蓋部９ａの下面が単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分に対応する位置に来るようにし、蓋部９ａの中央部分に形成された開口部９ｂは、上に行くに従って漸次拡径するテーパ状の開口とする。これにより、単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分から上方への放射熱が遮断されると共に、単結晶１５のテーパ部１５ａが厚みのある耐火物９の蓋部９ａで囲まれて保温されるのを防ぐことができる。
【００５８】
また、本実施形態では、伝熱部材として、ルツボ１の側壁１ａ外面を囲み、ルツボ１よりも高さが高い円筒状の伝熱部材３を示したが、伝熱部材は、このような構成に限らず、ルツボ１またはルツボ１近傍の熱を上方に伝えることができれば様々な構成にすることができる。例えば、図３に示すように、ルツボ１の上端部分近傍に下端部分が位置し、上端部分が冷却過程における単結晶１５の直胴部１５ｂの途中の高さまでとすることもできる。このように伝熱部材は、ルツボ１と接触していたり、ルツボ１を囲んでいる必要はなく、また、高さも境界部分放射熱遮断体を設けたか否かなどの条件などにより適宜選択できる。
【００５９】
また、本実施形態では境界部分放射熱遮断体となる放射熱遮断部材７と伝熱部材３との両方を設けた構成を示したが、境界部分放射熱遮断体と伝熱部材とはいずれか一方だけを設けても、本発明の効果を得ることができる。ここで、境界部分放射熱遮断体のみを設けた場合の効果を数値シミュレーションにより計算した例を示す。計算条件として、結晶材料を融点１９５０℃のＧｄ２ＳｉＯ５とし、図１に示すような放射熱遮断部材７が有る場合と無い場合の結晶内温度分布を計算した。計算の結果、冷却過程の単結晶１５の中央部分の高さにおける半径方向の温度差が、放射熱遮断部材７が無い場合には５０℃程度であるのに対し、放射熱遮断部材７が有る場合には３５℃程度になった。このように、境界部分放射熱遮断体のみを設けても冷却過程における単結晶の半径方向の温度差を低減でき、熱応力による割れなどを防止し、不良率の低減や、品質の向上などが可能となる。ただし、境界部分放射熱遮断体と伝熱部材との両方を設ければ、いずれか一方をを設けた場合よりもこれらの効果を向上できる。
【００６０】
（第２の実施形態）
以下、本発明を適用してなる単結晶製造技術の第２の実施形態について図４を参照して説明する。図４は、本発明を適用してなる単結晶の製造装置の概略構成を育成過程の状態で示す縦断面図である。なお、本実施形態では、第１の実施形態と同一のもの及び動作などには同じ符号を付して説明を省略し、第１の実施形態と相違する構成及び特徴部などについて説明する。
【００６１】
本実施形態の単結晶製造技術が第１の実施形態と相違する点は、境界部分放射熱遮断体を上下方向に移動可能としたことにある。すなわち、本実施形態の単結晶の製造装置は、図４に示すように、中央部分に単結晶１５の直胴部１５ｂの径に対応する貫通穴２７が形成された円盤リング状の放射熱遮断部材２９、放射熱遮断部材２９を支持すると共に上下方向に移動させる境界部分放射熱遮断体移動手段などを備えている。境界部分放射熱遮断体となる放射熱遮断部材２９は、円盤の面を上下方向に向けた状態で、境界部分放射熱遮断体移動手段を構成する棒状の支持部材によって支持されている。境界部分放射熱遮断体移動手段は、放射熱遮断部材２９を支持し、容器１９の天井に形成された貫通穴に挿通されて上下方向に延在する棒状の支持部材３１、容器１９の外側に設けられて支持部材３１を上下方向に移動させるための図示していない移動機構などで構成されている。
【００６２】
このような本実施形態では、放射熱遮断部材２９は、冷却過程だけでなく、育成過程においても単結晶１５のテーパ部１５ａと直胴部１５ｂとの境界部分に対応する位置に位置し、単結晶１５の成長と共に上方に移動する。この結果、育成過程と冷却過程の両者において、放射熱遮断部材２９の作用により単結晶１５の半径方向の温度差が低減され、単結晶の製造における不良率を低減できる。
【００６３】
さらに、品質の向上や生産能力の向上といった効果も得られる。
【００６４】
なお、製造する単結晶の種類などの条件によって、育成過程には放射熱遮断部材２９を単結晶１５や耐火物９から離して装置上部に移動させ、冷却過程のみに単結晶１５の境界部分に位置させるような動作を行うこともできる。この場合、育成過程では放射熱遮断部材２９による放射熱遮蔽作用がないため、単結晶１５の周囲からの放熱により、成長速度を大きくでき、冷却過程のみに単結晶１５の半径方向の温度分布を均一化させられる。製造する単結晶の種類などの条件によっては、単結晶１５の育成過程では結晶の半径方向の温度差が生じるが、結晶の材料物性として融点に近い場合には流動性があり欠陥や割れなどが発生し難い場合もある。
【００６５】
（第３の実施形態）
以下、本発明を適用してなる単結晶製造技術の第３の実施形態について図５乃至図７を参照して説明する。図５は、本発明を適用してなる単結晶の製造装置の概略構成を育成過程におけるテーパ部形成時の状態で示す縦断面図である。図６は、単結晶のテーパ部形成時における放射熱遮断筒の配置がわかるように示したルツボ近傍の斜視図である。図７は、図５に示す単結晶の製造装置の育成過程における直胴部形成時の状態を示す縦断面図である。なお、本実施形態では、第１及び第２の実施形態と同一のもの及び動作などには同じ符号を付している。
【００６６】
本実施形態の単結晶の製造装置は、図５に示すように、軸線を上下方向にして配置された、縦断面が矩形の円筒状の容器１９と、容器１９の底面１９ａ上面に支持部材２１で支持され容器１９と同心状に配置された円筒状の断熱材である耐火物９と、耐火物９の底面９ａ上に耐火物９と同心状に配置されたルツボ１と、容器１９の上面１９ｂの中心部分に形成された開口に挿通され、耐火物９の中心線上を上下動可能に配置された棒状及び帯状のシードホルダー１７を含む結晶移動手段と、シードホルダー１７の下端に装着された種結晶１３と、棒状または帯状のシードホルダー１７と同心状に配置され、耐火物９の中心線に沿って上下動可能に構成されたルツボ内放射熱遮断体となる放射熱遮断筒３３と、容器１９の上面１９ｂに形成された開口に挿通され、放射熱遮断筒３３を耐火物９の中心線に沿って上下に移動させるルツボ内放射熱遮断体移動手段となる放射熱遮断筒移動手段と、耐火物９の下部外周に耐火物９と同心状に巻回されたルツボ１の高周波誘導加熱用の高周波コイル１１とを含んで構成されている。
【００６７】
容器１９は、上下が閉じられた円筒状をなし、上面１９ｂに前記シードホルダー１７が挿通される開口、及び放射熱遮断筒移動手段が有する棒状の放射熱遮断筒３３の支持部材３５が挿通される開口が形成されている。耐火物９は、下端が底面９ａで閉じられ、上部が開放された円筒状をなしている。また、高周波コイル１１は、ルツボ１の全体を加熱するように、耐火物９の下端部分から、ルツボ１の上端部分に対応する耐火物９の外周面位置よりも上の方にまで、巻回されている。ルツボ１には、単結晶の材料である融液２５が、ルツボ１の上端よりも少し低い位置に液面が来る程度に満たされる。
【００６８】
放射熱遮断筒３３は、非金属材料、例えば結晶材料と同じ材料などで作られ、図６に示すように、内径が製品単結晶の直胴部の径と同じかそれより大きい、短い筒状をなしている。なお、結晶移動手段は、シードホルダー１７、シードホルダー１７を上下方向に移動させるための図示していない移動機構などで構成されている。同様に、ルツボ内放射熱遮断体移動手段は、支持部材３５、支持部材３５を上下方向に移動させるための図示していない移動機構などで構成されている。
【００６９】
このような構成の単結晶の製造装置の動作と本発明の特徴部について説明する。高周波コイル１１への通電によってルツボ１の近傍に高周波が発生し、金属製のルツボ１が発熱する。ルツボ１が高温となり結晶材料の融液２５を高温にする。種結晶１３の下端部が融液２５に接触され、種結晶１３に接触した融液２５は種結晶１３とシードホルダー１７を経た熱伝導によって冷却され、種結晶１３が結晶材料の融点以下になっているため、融液２５に接触している種結晶１３の表面に新しい結晶つまり単結晶１５が成長する。新しい結晶の成長につれて種結晶１３はシードホルダー１７によって上方に引き上げられるが、種結晶１３及び単結晶１５の表面から放射伝熱によって容器１９の天井部及び耐火物９の内面に放熱するとともに、種結晶１３とシードホルダー１７とを経た熱伝導によって冷却され、単結晶１５が結晶材料の融点以下になっているため、融液２５に接触している単結晶１５の表面に新しい結晶が成長する。
【００７０】
単結晶の成長初期のテーパ部形成時には、図５に示すように、単結晶１５の直径を次第に大きくするように、単結晶１５の上部表面は円錐形に末広がりのテーパ形状をなすテーパ部１５ａが形成される。この段階では、テーパ部１５ａのテーパ面が、融液２５の液面より上方のルツボ内面３７に直接対面しないように、ルツボ内面３７と単結晶１５のテーパ部１５ａのテーパ面との間になる位置に、放射熱遮断筒３３が、種結晶１３、即ちシードホルダー１７と同心状に移動、配置される。放射熱遮断筒３３の軸方向の長さは、テーパ部形成時に融液２５の液面が最も低下したときでも、テーパ部１５ａのテーパ面の最上部からテーパ部１５ａのテーパ面の最下部まで、ルツボ内面３７からの放射熱がテーパ部１５ａのテーパ面に到達することが防げるような長さにしてある。
【００７１】
ルツボ１の発熱は融液２５に接している部分と融液２５より上方にある部分の両方で生じるが、図５に示したテーパ部形成時には、放射熱遮断筒３３によって高温のルツボ内面３７からテーパ部１５ａのテーパ面への放射熱が遮断されるため、テーパ部１５ａのテーパ面を低温に保つことができ、テーパ面の熱エッチングによる表面粗れを生じることがない。放射熱遮断筒３３は非金属材料製であるため、高周波加熱されない。
【００７２】
単結晶１５の直径が大きくなり、所定の大きさに達すると、図７に示すように、テーパ部１５ａの形成が終わり、直胴部形成に移る。直胴部形成では、円柱状に単結晶１５が長く育成され直胴部１５ｂが形成される。このとき、放射熱遮断筒３３はルツボ１や単結晶１５から離れて容器１９の上部に移動し、単結晶１５の直胴部１５ｂの外周面はルツボ内面３７に直接対面している。
【００７３】
直胴部形成に移った時に、図７に示すように、放射熱遮断筒３３を上方に移動させるから、単結晶１５の直胴部１５ｂの外周面は、高温のルツボ内面３７に直面し、ルツボ内面３７の放射熱により加熱される。その加熱量によって、単結晶１５の直胴部１５ｂの外周面から容器１９の天井部や耐火物９への放熱量が相殺されるため、単結晶１５の半径方向に温度差が低減され、融液２５に接触している単結晶１５の表面１５ｃにおいて均一に結晶が成長する。直胴部形成時には、ルツボ１の上方に出ている結晶部分、つまりテーパ部１５ａのテーパ面からの放熱が大きいため、単結晶１５の直胴部１５ｂの外周面のルツボ内部分がルツボ内面３７に直接対面していても高温とならず、直胴部１５ｂの外周面に熱エッチングによる表面粗れが生じることはない。これらの作用によって割れつまりクラックなどを発生させることなく、不良率を低減でき、さらに、品質を向上した単結晶の成長が可能になる。
【００７４】
本実施の形態の効果を数値シミュレーションにより計算した。計算条件として、結晶材料を融点１９５０℃のＧｄ２ＳｉＯ５とし、図５と図７に示す本実施形態のようにテーパ部形成時におけるルツボ内放射熱遮断体である放射熱遮断筒３３の有無による温度変化を計算した。結晶下部の結晶成長面の温度を融点１９５０℃とする。計算の結果、テーパ部形成時において図５に示すように放射熱遮断筒３３を入れると、テーパ部１５ａのテーパ面は約１７３０℃となる。このとき、放射熱遮断筒３３の反射率を１．０とする。仮に放射熱遮断筒３３がないとするとテーパ部１５ａのテーパ面は約１７８０℃となり、放射熱遮断筒、つまりルツボ内放射熱遮断体の有無によってテーパ面は５０℃程度の差がある。
【００７５】
このように、本実施形態の単結晶の製造技術によれば、テーパ部形成時のテーパ面温度を低減でき、熱エッチングによるその表面の粗れを低減でき、テーパ面を発生源とした欠陥や割れの発生を低減できる。したがって、単結晶の製造における不良率を低減できる。
【００７６】
さらに、本実施形態では、結晶の直胴部形成時において結晶の面内を均一に成長させることができ、また成長速度を大きくすることが可能である。さらに本発明は結晶成長の制御性を向上する効果もある。
【００７７】
（第４の実施形態）
以下、本発明を適用してなる単結晶製造技術の第４の実施形態について図８及び図９を参照して説明する。図８は、本発明を適用してなる単結晶の製造装置の概略構成を育成過程におけるテーパ部形成時の状態で示す縦断面図である。図９は、本実施形態の直胴部形成時のルツボ近傍の状態を示す縦断面図である。なお、本実施形態では、第３の実施形態と同一のもの及び動作などには同じ符号を付して説明を省略し、第３の実施形態と相違する構成及び特徴部などについて説明する。
【００７８】
本実施形態が第３の実施形態と相違する点は、放射熱遮断筒移動手段と放射熱遮断筒に代えて、ルツボと同じ金属材料などからなる環状の直胴部放射熱遮断体と、直胴部放射熱遮断体を耐火物の中心線に沿って上下方向に移動させる直胴部放射熱遮断体移動手段を設けたことにある。すなわち、本実施形態の単結晶の製造装置は、図８に示すように、ルツボ１と同じ金属材料などからなる環状の直胴部放射熱遮断体となる放射熱遮蔽板３９、放射熱遮蔽板３９を耐火物９の中心線に沿って上下方向に移動させる直胴部放射熱遮断体移動手段などを備えている。
【００７９】
直胴部放射熱遮断体移動手段は、放射熱遮蔽板３９を支持する棒状の支持部材４１、支持部材４１を上下方向に移動させるための図示していない移動機構などで構成されている。また、高周波コイル１１は、その上端部がルツボ１の上端部分よりも低くなるように全体として第３の実施形態に比べて下に下げられており、ルツボ１の融液２５の液面より上の部分の加熱量が第３の実施の形態よりも少なくなっている。
【００８０】
放射熱遮蔽板３９は、単結晶１５のテーパ部形成時には耐火物９の上端よりも上方に位置させ、単結晶１５の直胴部形成時にはルツボ１上部の単結晶周囲に位置させる。したがって、放射熱遮蔽板３９は、外径がルツボ１の内径とほぼ同じかそれよりも小さく、内径が育成される単結晶１５の直胴部１５ｂの外径よりも僅かに大きくなっている。
【００８１】
高周波コイル１１への通電によってルツボ１が加熱されるが、この加熱は、高周波コイル１１が全体として第３の実施形態に比べて下に下げられているため、ルツボ１の融液２５の液面より上方部分の加熱量が少なくなっている。そして、本実施形態では、単結晶１５のテーパ部形成時には、図８に示すように、放射熱遮蔽板３９が、支持部材４１を含む直胴部放射熱遮断体移動手段によって容器１９の上部、耐火物９の上端よりも上方に移動している。
【００８２】
すなわち、テーパ部形成時には、放射熱遮蔽板３９がないため、単結晶１５のテーパ部１５ａのテーパ面から上方に放熱し、テーパ部１５ａのテーパ面をより低い温度に保つことができる。テーパ部１５ａのテーパ面は、ルツボ１の内面と直接対向するが、ルツボ１の融液２５の液面より上方部分の高周波コイル１１による加熱量が少なくなっているので、テーパ部１５ａのテーパ面の放熱量に比べて加熱量が少なく、テーパ部１５ａのテーパ面は低温に保たれ、高温による表面粗れが避けられる。
【００８３】
テーパ部１５ａのテーパ面の形成が終わり、直胴部形成の過程では、図９に示すように、放射熱遮蔽板３９が図８に示された位置から下方に下げられ、ルツボ１上部の単結晶１５の直胴部１５ｂ周囲に、ルツボ１上端と単結晶１５の直胴部１５ｂの外周面との間を塞ぐように、配置される。このため、ルツボ１の内部にある単結晶１５の直胴部１５ｂの外周面からの放熱が小さくなり、単結晶１５の半径方向の温度差が低減され、欠陥や割れなどの発生が低減され、単結晶の製造における不良率が低減される。
【００８４】
さらに、融液２５に接触している単結晶１５の表面１５ｃの全面において均一に結晶が成長する。加えて、テーパ部１５ａのテーパ面からの放熱を遮るものがないので、結晶成長面の冷却の速度が速くなり、結晶成長速度を大きく保つことができる。さらに、放射熱遮蔽板３９は金属製であるため、放射熱遮蔽板２１においても高周波加熱にて高温となり、ルツボ１の内部を加熱する効果もある。
【００８５】
なお、図９では、放射熱遮蔽板３９がルツボ１上部の単結晶１５の直胴部１５ｂ周囲に、ルツボ１上端と単結晶１５の直胴部１５ｂ外周面の間を塞ぐように配置されており、この位置が最も直胴部１５ｂの外周面からの放熱を抑止するので望ましい。しかし、放射熱遮蔽板３９を更に下げ、ルツボ１の内部になる位置に配置しても、融液２５の液面に近い位置の直胴部１５ｂの外周面の温度降下を抑止することができるから、図９に示す位置の場合とほぼ同様の効果が得られる。
【００８６】
放射熱遮蔽板３９を、内径が単結晶１５の直胴部１５ｂの外径よりも大きくてルツボ１の内径よりも小さく、かつ外径がルツボ１の外径よりも大きい環状体とし、このような放射熱遮蔽板を、単結晶直胴部形成時に、ルツボ１上端部に近接して位置させ、単結晶１５のテーパ部形成時にはルツボ１上端部分から上方に離れた位置に移動させるようにすることでも、同様の効果がある。
【００８７】
（第５の実施形態）
以下、本発明を適用してなる単結晶製造技術の第５の実施形態について図１０及び図１１を参照して説明する。図１０及び図１１は、本発明を適用してなる単結晶の製造装置の概略構成を育成過程におけるテーパ部形成時の状態で示すルツボ近傍の縦断面図である。なお、本実施形態では、第３及び第４の実施形態と同一のもの及び動作などには同じ符号を付して説明を省略し、第３及び第４の実施形態と相違する構成及び特徴部などについて説明する。
【００８８】
本実施の形態が第３の実施形態と相違する点は、図５に示す放射熱遮断筒３３と放射熱遮断筒移動手段に代えて、単結晶のテーパ部のテーパ形状に沿った円錐形状の非金属材料のルツボ内放射熱遮断体と、ルツボ内放射熱遮断体を耐火物の中心線に沿って上下させるルツボ内放射熱遮断体移動手段を設けたことにある。すなわち、本実施形態の単結晶の製造装置は、図１０に示すように、単結晶１５のテーパ部１５ａのテーパ形状に沿った円錐形状の非金属材料のルツボ内放射熱遮断体である放射熱遮断板４３、放射熱遮断板４３を支持する棒状の支持部材４５を含んで放射熱遮断板４３を耐火物９の中心線に沿って上下させるルツボ内放射熱遮断体移動手段を備えている。ルツボ内放射熱遮断体移動手段は、放射熱遮断板４３を支持して上下方向に延在する棒状の支持部材４５、支持部材４５を上下方向に移動させるための図示していない移動機構などで構成されている。
【００８９】
本実施形態では、単結晶１５のテーパ部形成時には、図１０に示すように、単結晶１５のテーパ部１５ａのテーパ面の近くに放射熱遮断板４３が位置される。放射熱遮断板４３の円錐面の傾斜角度は、テーパ部１５ａのテーパ面の傾斜角度とほぼ同じになっている。また、図１１に示すように、単結晶１５の直胴部形成時には、放射熱遮断板４３は単結晶１５のテーパ部１５ａのテーパ面から離れた位置に移動している。
【００９０】
このような本実施形態の放射熱遮断板４３の動作は、第３の実施形態の放射熱遮断筒３３の動作と同様であり、単結晶１５のテーパ部形成時には単結晶１５のテーパ部１５ａのテーパ面の近くに放射熱遮断板４３が配置され、単結晶１５の直胴部形成時には、放射熱遮断板４３は単結晶１５のテーパ部１５ａのテーパ面から離れた位置に移動させられている。
【００９１】
本実施形態では、放射熱遮断板４３の円錐面の傾斜角度がテーパ部１５ａのテーパ面の傾斜角度とほぼ同じであるため、テーパ部形成時に、テーパ部１５ａのテーパ面のどの位置でも、テーパ部１５ａのテーパ面と放射熱遮断板４３の間隔が同じ状態でテーパ部１５ａが形成されるため、テーパ部１５ａのテーパ面の全面を均一に形成でき、クラックつまり割れの発生源が生じ難くなり、単結晶の製造における不良率を低減できる。
【００９２】
加えて、直胴部形成時には放射熱遮断板４３がテーパ部１５ａのテーパ面に近接した位置にないため、テーパ部１５ａのテーパ面からの放熱を大きくして成長速度を大きくすることができる。
【００９３】
すなわち、本実施形態によっても、他の実施形態と同様の効果が得られる。
【００９４】
なお、放射熱遮断板４３として、図１０のような円錐板だけでなく、平円板を用いても表面粗れ防止の効果が得られるが、形成するテーパ部のテーパ面の傾斜に合った円錐板を用いるのが望ましい。
【００９５】
（第６の実施形態）
本発明を適用してなる単結晶の製造装置の第６の実施形態について図１２乃至図１５を参照して説明する。図１２は、本発明を適用してなる単結晶の製造装置の概略構成と動作を示す縦断面図であり、単結晶のテーパ部の育成段階を示す図である。図１３は、本発明を適用してなる単結晶の製造装置の概略構成と動作を示す縦断面図であり、単結晶の直胴部の育成段階を示す図である。図１４は、本発明を適用してなる単結晶製造装置と、従来の単結晶製造装置の側壁の高さ方向における発熱量の分布を比較した図である。図１５は、本発明を適用してなる単結晶製造装置と、従来の単結晶製造装置の側壁の高さ方向における温度分布を比較した図である。なお、本実施形態では、第１乃至第５の実施形態と同一のもの及び動作などには同じ符号を付している。
【００９６】
本実施形態の単結晶の製造装置は、図１２に示すように、円筒状のルツボ１、ルツボ１の側壁外面に取り付けられて壁側加熱部材となるリング状部材４７、ルツボ１を取り囲む耐火物９、耐火物９の外側で高周波を発生する高周波発生手段４９、そして種結晶を保持すると共に結晶を回転させながら上方に引き上げる結晶移動手段５１などで構成されている。
【００９７】
本実施形態の単結晶の製造装置は、融点が１５００℃以上の単結晶の製造装置であり、ルツボ１は、上端部分１ｃが開口され、下端部分１ｄが閉塞されて底１ｂが形成された円筒状の容器であり、導電性を有し高融点の金属材料、例えばイリジウム、白金、タングステン、モリブデンなどで形成されている。リング状部材４７は、ルツボ１の側壁１ａの外面に、この側壁１ａの外面の周方向に沿ってリング状に設けられており、側壁１ａ外面から横方向に突出した状態の突起状の部材である。
【００９８】
このようなリング状部材４７は、ルツボ１と同様に導電性を有し高融点の金属材料、例えばイリジウム、白金、タングステン、モリブデンなどで形成されており、ルツボ１と一体に形成することもできるし、ルツボ１と別体で形成したものをルツボ１の側壁に取り付けることもできる。リング状部材４７をルツボ１と別体で形成した場合、リング状部材４７は、ルツボ１を形成した材料と同じ材料で形成することもできるし、異なる材料で形成することもできる。また、リング状部材４７をルツボ１と別体で形成した場合、リング状部材４７は、ルツボ１とできるだけ強く接触した状態で取り付けることが望ましい。なお、本実施形態では、リング状部材４７は、ルツボ１の側壁１ａ外面の上端部分１ｃと下端部分１ｄとの間の部分に、間隔をおいて２つ設けられている。
【００９９】
耐火物９は、上端部分が開口され、下端部分が閉塞されて底が形成されたルツボ１よりも大きな円筒状の容器であり、絶縁性と断熱性を有する高温耐性の材料、例えばジルコニアやアルミナなどで形成されており、内部にリング状部材４７が設けられたルツボ１を収容している。高周波発生手段４９は、耐火物９の外側で、ルツボ１の側壁１ａに対応する位置に、この耐火物９の外側を取り囲んで設置された高周波コイル１１や、高周波コイル１１と配線５３を介して電気的に接続された高周波電源５５などで構成されている。結晶移動手段５１は、棒状または帯状のシードホルダー１７、シードホルダー１７が垂下されると共に、シードホルダー１７を回転させながら引き上げる駆動部５７などで構成されている。駆動部５７は、耐火物９の上端部分の開口上方からルツボ１の開口の中央部分に向けてシードホルダー１７が垂下された状態でシードホルダー１７を支持しており、シードホルダー１７のルツボ１側の先端部分に種結晶１３が取り付けられる。
【０１００】
このような構成の単結晶の製造装置の動作と本発明の特徴部について説明する。ルツボ１内に原料を収容した状態で、高周波電源５５から高周波電流を高周波コイル１１に流すと、導電性のルツボ１に誘導電流が流れる。これにより、ジュール加熱によってルツボ１が加熱され、昇温したルツボ１内の原料が溶解され溶融状態となり、融液２５となる。シードホルダー１７の先端部に付けた種結晶１３を融液２５から引き上げると、単結晶１５が生成される。単結晶１５が生成されるとき、最初、種結晶１３に連続して円錐状にテーパ部１５ａが形成され、テーパ部１５ａに連続して、図１３に示すように、円柱状の直胴部１５ｂが形成される。なお、単結晶１５を融液２５から引き上げて行くとき、融液２５の液面近傍に単結晶１５からルツボ１の側壁１ａの内面に向かう流れ、つまり単結晶１５の位置から半径方向に拡がる流れを生じさせるため、シードホルダー１７を回転軸として回転させることで単結晶１５を回転させている。
【０１０１】
ここで、高周波コイル１１によって発生した電磁界は、特に角部に集中するため、ルツボ１の上端部分１ｃ及び下端部分１ｄで他の部分よりも大きく発熱する。さらに、本実施形態では、ルツボ１の側壁１ａ外面の上端部分１ｃと下端部分１ｄとの間の部分に設置されているリング状部材４７も、ルツボ１の上端部分１ｃ及び下端部分１ｄと同様に他の部分よりも大きく発熱する。
【０１０２】
したがって、単位体積量当たりの側壁１ａの発熱量は、図１４の実線で示した発熱量分布１０１で示すように、ルツボ１の底１ｂから上端部分１ｃ方向つまり高さ方向に向かって順に、側壁１ａの底１ｂの周縁部分つまり下端部分１ｄ、下側に位置するリング状部材４７が設けられた部分、上側に位置するリング状部材４７が設けられた部分、そして側壁１ａの上端部分１ｃでピークとなるように分布する。この結果、ルツボ１の側壁１ａの温度分布も、図１５の実線で示した温度分布１０５で示すように、ルツボ１の底１ｂから上端部分１ｃ方向つまり高さ方向に向かって順に、側壁１ａの底１ｂの部分、下側に位置するリング状部材４７が設けられた部分、上側に位置するリング状部材４７が設けられた部分、そして側壁１ａの上端部分１ｃでピークとなる。
【０１０３】
ところで、リング状部材４７が設けられていない従来の単結晶の製造装置では、単位体積量当たりの側壁の発熱量は、図１４の破線で示した発熱量分布１０３で示すように、ルツボの底から上端部分方向つまり高さ方向に向かって順に、側壁の底の周縁部分つまり下端部分、そして側壁の上端部分のみでピークとなるように分布する。この結果、ルツボの側壁の温度分布も、図１５の破線で示した温度分布１０７で示すように、ルツボの底から上端部分方向つまり高さ方向に向かって順に、側壁の底の周縁部分、そして側壁の上端部分のみでピークとなる。すなわち、従来の単結晶の製造装置では、側壁の下端部分と上端部分の発熱量と温度が他の部分よりも高くなり、発熱量と温度の分布が不均一な状態になっている。側壁の下端部分と上端部分の距離が長くなるに連れ、側壁の下端部分と上端部分との間の部分の発熱量と温度は低下して行くため、このような発熱量と温度の分布が不均一な状態は、特に底の直径に比べて高さの方が高いルツボや、底の直径及び高さが数十センチ以上といった大型のルツボを使用する際に大きくなる。
【０１０４】
したがって、従来の単結晶の製造装置では、ルツボの大きさや形状などの条件によって、側壁１ａの高さ方向における発熱量及び温度の分布が不均一で側壁１ａの下端部分１ｄと上端部分１ｃとの間の部分の温度が低いと、図１６に示すように、ルツボ１内の融液２５は、ルツボ１の下端部分１ｄで加熱されて膨張し、最初ルツボ１の側壁１ａ内面に沿って上昇するが、ルツボ１の側壁１ａの中ほどの高さでは温度が低くなるため、側壁１ａから離れるように流れ、ルツボ１内の上部の融液２５の流れと干渉し、複雑な対流パターンを呈し、ルツボ１内の融液２５全体の流れが乱れる。
【０１０５】
これにより、種結晶１３に連続して形成された単結晶１５の単結晶育成部分つまり固液界面部分５９の形状が乱れて凹凸状態となってしまう。単結晶１５の固液界面部分５９の形状が乱れて凹凸状態となってしまうと、単結晶１５の固液界面部分５９やその近傍部分の温度分布が不均一となり、単結晶１５内に歪が生じるなど、単結晶１５の品質が悪くなる。また、単結晶１５内に歪が生じると、育成した単結晶１５の冷却時に、結晶が割れるなどの問題も発生する。
【０１０６】
これに対して、本実施形態の単結晶の製造装置では、上述のように、ルツボ１にリング状部材４７が設けられたことにより、側壁１ａにおける発熱量は、側壁１ａの下端部分１ｄと上端部分１ｃに加えて、下側のリング状部材４７が設けられた部分と上側のリング状部材４７が設けられた部分で他の部分よりも高くなる。そして、下側のリング状部材４７が設けられた部分と上側のリング状部材４７が設けられた部分の発熱量が高くなることによって、側壁１ａの下端部分１ｄ、下側のリング状部材４７が設けられた部分、上側のリング状部材４７が設けられた部分、そして上端部分１ｃ以外の部分の発熱量も従来の単結晶の製造装置よりも高くなっており、従来の単結晶の製造装置に比べ、側壁の高さ方向の発熱量分布が均一化されている。
【０１０７】
これにより、本実施形態の単結晶の製造装置では、側壁１ａにおける温度は、側壁１ａの下端部分１ｄと上端部分１ｃに加えて、下側のリング状部材４７が設けられた部分と上側のリング状部材４７が設けられた部分で他の部分よりも高くなる。そして、下側のリング状部材４７が設けられた部分と上側のリング状部材４７が設けられた部分の温度が高くなることによって、側壁１ａの下端部分１ｄ、下側のリング状部材４７が設けられた部分、上側のリング状部材４７が設けられた部分、そして上端部分１ｃ以外の部分の発熱量も従来の単結晶の製造装置よりも高くなっており、従来の単結晶の製造装置に比べ、側壁の高さ方向の温度分布が均一化されている。このようにルツボ１の側壁１ａの高さ方向における発熱量及び温度の分布が均一化すると、図１２び図１３に示すように、ルツボ１内の融液２５に、自然対流でルツボ１の側壁１ａの内面に沿って滑らかに上昇する流れを形成するため、従来の単結晶の製造装置のように、望ましくない複雑な対流パターンを呈し難い。
【０１０８】
このように、本実施形態の単結晶の製造装置では、側壁１ａの下端部分１ｄと上端部分１ｃとの間の部分にリング状部材４７が設けられているため、上述のように、高周波発生手段４９の駆動により、側壁１ａの下端部分１ｄと上端部分１ｃに加えて、下側のリング状部材４７と上側のリング状部材４７も発熱し、ルツボ１の側壁１ａの高さ方向における温度分布が均一化する。このため、ルツボ１の側壁１ａの高さ方向の発熱分布を制御し、ルツボ１内の融液２５の対流を制御することができ、ルツボ１内の融液２５に自然対流でルツボ１の側壁１ａの内面に沿って滑らかに上昇する流れを形成できるため、ルツボ１内の融液２５が従来のような望ましくない対流パターンを呈し難い。したがって、ルツボの大きさや形状などの条件に関係なく単結晶の固液界面部分を平坦化でき、欠陥や割れなどの発生を低減して、単結晶の製造における不良率を低減することができる。
【０１０９】
さらに、単結晶の固液界面部分を平坦化できることにより、得られる単結晶の品質を向上でき。加えて、単結晶の品質を向上でき、また、結晶の割れなどの発生を抑えることができることにより、単結晶の生産性を向上できる。
【０１１０】
また、本実施形態では、リング状部材４７を上下２段に設けているが、リング状部材４７は、１段にすることもでき、また、３段以上設けることもできる。リング状部材４７を設ける段数は、ルツボの大きさなどに応じて適宜決定する。
【０１１１】
また、本実施形態では、壁側加熱部材としてルツボ１の側壁１ａ外面の円周方向に設けられたリング状部材４７を用いているが、壁側加熱部材は、ルツボ１の側壁１ａ外面の円周方向に延在していれば一連のリング状の形態である必要はなく、様々な形態にすることもできる。例えば、壁側加熱部材は、ルツボ１の側壁１ａ外面の円周方向に適当な間隔をおいて断続的にリング状に連なる部材片などで構成することもできる。この場合、部材片は、ルツボ１の側壁１ａの高さ方向よりも側壁１ａ外面の円周方向に長く延在する形状にする必要があり、さらに、ルツボ１の側壁を均一に加熱するため、このような部材片を等間隔で設けることが望ましい。
【０１１２】
（第７の実施形態）
以下、本発明を適用してなる単結晶の製造装置の第７の実施形態について図１７及び図１８を参照して説明する。図１７は、本発明を適用してなる単結晶の製造装置の概略構成と動作を示す断面図であり、単結晶のテーパ部の育成段階を示す図である。図１８は、本発明を適用してなる単結晶製造装置と、従来の単結晶製造装置の底の温度分布を比較した図である。なお、本実施形態では、第６の実施形態と同一のもの及び動作などには同じ符号を付して説明を省略し、第６の実施形態と相違する構成及び特徴部などについて説明する。
【０１１３】
本実施形態の単結晶の製造装置が第６の実施形態と相違する点は、壁側加熱部材であるリング状部材に加えて、ルツボの底の中央部分を加熱するための底側加熱部材を設けたことにある。すなわち、本実施形態の単結晶の製造装置は、図１７に示すように、ルツボ１の底１ｂ外面の中央部分に設けられた円柱状または円盤状の部材からなる伝熱部６１、そして伝熱部６１が中央部分に設けられた円盤状の発熱部６３で構成された底側加熱部材６５を備えている。発熱部６３は、伝熱部６１の直径よりも大きな直径であり、さらにルツボ１の底１ｂが有する直径の２／３以上の直径で形成されている。このように発熱部６３の直径をルツボ１の底１ｂの直径の２／３以上とすることで発熱部６３が高周波電磁界で発熱し易くなり、底側加熱部材６５の加熱能力を向上できる。なお、ルツボ１の底１ｂ側に設けられた底側加熱部材６５は、ルツボ１と共に耐火物９内に収容されている。
【０１１４】
伝熱部６１と発熱部６３で構成された底側加熱部材６５は、ルツボ１及びリング状部材４７と同様に導電性を有し高融点の金属材料、例えばイリジウム、白金、タングステン、モリブデンなどで形成されており、ルツボ１の底１ｂに連続させてルツボ１と一体に形成することもできるし、ルツボ１と別体で形成したものをルツボ１の底１ｂに取り付けることもできる。さらに、底側加熱部材６５の伝熱部６１と発熱部６３とを別体で形成することもできる。底側加熱部材６５をルツボ１と別体で形成した場合、底側加熱部材６５は、ルツボ１を形成した材料と同じ材料で形成することもできるし、異なる材料で形成することもできる。また、底側加熱部材６５をルツボ１と別体で形成した場合、底側加熱部材６５は、伝熱部６１がルツボ１とできるだけ強く接触した状態で取り付けることが望ましい。
【０１１５】
このような構成の本実施形態の単結晶の製造装置では、高周波コイル１１によって発生した電磁界は、特に角部に集中するため、ルツボ１の底１ｂの周縁部分、つまりルツボ１の下端部分１ｄに加えて、底側加熱部材６５の発熱部６３の周縁部分でも発熱する。底側加熱部材６５の発熱部６３の周縁部分で発熱した熱は、熱伝導により、伝熱部６１を介して発熱部６３からルツボ１の底１ｂの中央部分に伝えられ、ルツボ１の底１ｂの中央部分が加熱される。したがって、単位体積量当たりの底１ｂの発熱量は、ルツボ１の底１ｂの周縁部分に加え、底１ｂの中央部分でもピークとなるように分布する。この結果、ルツボ１の底１ｂでの温度分布も、図１８の実線で示した温度分布２０１で示すように、ルツボ１の底１ｂの周縁部分に加え、底１ｂの中央部分でピークとなる。
【０１１６】
これに対して、底側加熱部材６５が設けられていない従来の単結晶の製造装置では、単位体積量当たりの底の発熱量は、ルツボ１の底の周縁部分のみでピークとなるように分布する。この結果、ルツボの側壁の温度分布も、図１８の破線で示した温度分布２０３で示すように、ルツボの底の周縁部分のみでピークとなる。すなわち、従来の単結晶の製造装置では、ルツボの底の中央部分が、温度が最も低い状態になっている。そして、ルツボの底の中央部分の温度は、ルツボの底の直径が大きくなるに連れて低くなって行く。したがって、従来の単結晶の製造装置では、ルツボの大きさや形状などの条件によって、ルツボの底の中央部分から上昇する融液の流れが形成されず、単結晶の固液界面部分からルツボの側壁内面に向かう半径方向に拡がる融液の流れが形成されない場合がある。このため、種結晶に連続して形成された単結晶の固液界面部分の形状が乱れて凹凸状態となり、品質の悪い結晶が生成されたり、結晶に割れが生じたりする。
【０１１７】
従来、ルツボの底の中央部分の温度が低く、単結晶の固液界面部分からルツボの側壁内面に向かう半径方向に拡がる融液の流れが形成されなくても、単結晶を引き上げる際に結晶を回転させることにより、単結晶からルツボの側壁内面に向けて半径方向に拡がる融液の流れを形成できるようにしている。ところが、種結晶から単結晶のテーパ部の生成段階においては、結晶を回転させても、種結晶や単結晶のテーパ部の直径が小さいため、結晶の回転により発生する遠心力も小さく、融液に半径方向に拡がる流れが、単結晶の直胴部が形成されはじめた後の段階よりも弱い。したがって、結晶の回転だけでは単結晶の固液界面部分を平坦化させることは困難である。このような状況は、第１の実施形態の単結晶の製造装置のように、壁側加熱部材のみをルツボに設けた場合であっても同様に生じる。
【０１１８】
これに対して、本実施形態の単結晶の製造装置では、図１７に示すように、ルツボ１に底側加熱部材６５が設けられたことにより、ルツボ１の底１ｂにおける発熱量は、底１ｂの周縁部分に加えて、中央部分でも他の部分よりも高くなる。そして、底１ｂの中央部分の発熱量が高くなることによって、ルツボ１の底１ｂの温度は、底１ｂの周縁部分に加えて、中央部分でも他の部分よりも高くなる。このように底１ｂの中央部分の温度が高くなると、底１ｂの中央部分からルツボ１の中心軸近傍をこの中心軸に沿って上昇して種結晶１３や単結晶１５の固液界面部分５９付近に到達し、種結晶１３や単結晶１５の固液界面部分５９付近からルツボ１の側壁１ａ内面に向かう半径方向に拡がる融液３１の流れが形成される。
【０１１９】
このように、本実施形態の単結晶の製造装置では、ルツボ１の底１ｂの中央部分を加熱する底側加熱部材６５が設けられているため、上述のように、高周波発生手段４９の駆動により、ルツボ１の底１ｂの周縁部分に加えて、中央部分も加熱する。このため、ルツボ１の底１ｂの中央部分から上昇して種結晶１３や単結晶１５の固液界面部分５９付近に到達し、種結晶１３や単結晶１５の固液界面部分５９付近からルツボ１の側壁１ａ内面に向かう半径方向に拡がる融液２５の流れが形成される。したがって、ルツボの大きさや形状などの条件に関係なく、単結晶の固液界面部分を平坦化でき、欠陥や割れなどの発生を低減して、単結晶の製造における不良率を低減することができる。
【０１２０】
また、本実施形態では、壁側加熱部材であるリング状部材４７を設けているが、ルツボの大きさや形状などの条件によって壁側加熱部材が不要な場合には、壁側加熱部材であるリング状部材４７を設けない構成にすることもできる。
【０１２１】
また、本実施形態では、円柱状または円盤状の部材からなる伝熱部６１、そして円盤状の発熱部６３で構成された底側加熱部材６５を備えているが、底側加熱部材は、高周波発生手段４９によって発熱し、ルツボ１の底１ｂの中央部分を加熱できる様々な構成にできる。
【０１２２】
例えば、図１９に示すように、耐火物９内の底面上に導電性を有し高融点の金属材料で形成した円盤上の部材を設置して発熱部６７とし、この発熱部６７に重ねて、中央部分に貫通穴６９が形成されて耐火物９の内径と同じ直径で形成された断熱部材７１を設置する。そして、ルツボ１の底１ｂの中央部分を断熱部材７１の貫通穴６９の位置に合わせてルツボ１を断熱部材７１上に設置する。このような底側加熱部材７３では、発熱部６７の周縁部分で発熱した熱は、熱伝導により発熱部６７の中央部分に集まり、貫通穴６９を介して輻射により、ルツボ１の底１ｂの中央部分を加熱する。このように、底側加熱部材は、底側加熱部材７３のような、伝熱部を形成する断熱部材７１と円盤上の部材である発熱部６７とで構成することもできる。底側加熱部材を底側加熱部材７３のような構成とすれば、部品点数を少なくできる。
【０１２３】
また、底側加熱部材は、発熱部を、導電性を有し高融点の金属材料で円形のリング状に形成し、この発熱部と同軸に導電性を有し高融点の金属材料で形成した円柱状の伝熱部を配置し、発熱部と伝熱部との間に高融点の金属材料で形成した棒状の連結部材をスポーク状に設ける構成などにもできる。なお、様々な構成の底側加熱部材において、伝熱部は、円盤状や円柱状である必要はなく、角柱状などにすることもできる。
【０１２４】
また、第６及び第７の実施形態では、壁側加熱部材であるリング状部材４７と底側加熱部材６５は、ルツボ１に固定された状態となっているが、壁側加熱部材と底側加熱部材を着脱自在な構成とし、不要な場合などにルツボから取り外すことができるようにすることもできる。さらに、壁側加熱部材と底側加熱部材をルツボ１に着脱する機構などを設けることもできる。例えば、図２０に示すように、耐火物９内の底９ｃの上方に中央部分に貫通穴７５が形成されて耐火物９の内径と同じ直径で形成された断熱部材７７を設置する。耐火物９内の底９ｃと断熱部材７７の間に、第７の実施形態と同じ構成で、ルツボ１とは別体に形成された底側加熱部材６５を設置する。但し、底側加熱部材６５の発熱部６３の下面には、耐火物９の底を貫通して設けられた連結部材７９が連結されている。連結部材７９は、底側加熱部材６５を上下移動させるための駆動部８１、例えば油圧またはエアジャッキや、モータ及びラックアンドピニオン式駆動機構などに連結されており、連結部材７９と駆動部８１は加熱部材移動手段８３を構成している。
【０１２５】
このような加熱部材移動手段８３を備えた構成とすれば、必要に応じて底側加熱部材６５の伝熱部６１をルツボ１の底１ｂから離脱させ、底１ｂの中央部分の加熱を停止することができる。つまり、種結晶１３から単結晶１５のテーパ部１５ａを形成する段階などでは、加熱部材移動手段８３により、底側加熱部材６５を押し上げて、底側加熱部材６５の伝熱部６１をルツボ１の底１ｂ接触させ、単結晶１５のテーパ部１５ａの径が十分大きくなったら、加熱部材移動手段８３により、底側加熱部材６５を下に下げて、底側加熱部材６５の熱がルツボ１の底１ｂの中央部分に伝熱しないようにする。なお、このような加熱部材移動手段を設けた構成を壁側加熱部材に適用することもできる。このように構成することにより、単結晶１５の固液界面部分５９を最適な状態に制御でき、より品質の高い単結晶を得ることができる。
【０１２６】
また、第１乃至第７の実施形態で示した単結晶の製造技術は、各々、適宜組み合わせて用いることができる。
【０１２７】
また、本発明は、第１乃至第７の実施形態の構成の製造装置に限らず、ルツボを高周波加熱する様々な構成の単結晶の製造装置に適用できる。さらに、本発明を適用してなる単結晶の製造装置は、特にガドリニウム、ガリウム、ガーネッド、セリウム付活珪酸ガドリニウムなどの酸化物単結晶の育成に有効であるが、その他の様々な種類の単結晶の製造に用いることができる。
【０１２８】
【発明の効果】
本発明によれば、単結晶の製造における不良率を低減できる。
【図面の簡単な説明】
【図１】本発明を適用してなる単結晶製造装置の第１の実施形態の概略構成を冷却過程の状態で示す縦断面図である。
【図２】本発明を適用してなる単結晶製造装置の第１の実施形態の概略構成を育成過程の状態で示す縦断面図である。
【図３】第１の実施形態の単結晶製造装置の変形例を示す縦断面図である。
【図４】本発明を適用してなる単結晶製造装置の第２の実施形態の概略構成を育成過程の状態で示す縦断面図である。
【図５】本発明を適用してなる単結晶製造装置の第３の実施形態の概略構成を育成過程におけるテーパ部形成時の状態で示す縦断面図である。
【図６】単結晶のテーパ部形成時における放射熱遮断筒の配置がわかるように示したルツボ近傍の斜視図である。
【図７】図５に示す単結晶の製造装置の育成過程における直胴部形成時の状態を示す縦断面図である。
【図８】本発明を適用してなる単結晶製造装置の第４の実施形態の概略構成を育成過程におけるテーパ部形成時の状態で示す縦断面図である。
【図９】第４の実施形態における直胴部形成時のルツボ近傍の状態を示す縦断面図である。
【図１０】本発明を適用してなる単結晶製造装置の第５の実施形態の概略構成を育成過程におけるテーパ部形成時の状態で示すルツボ近傍の縦断面図である。
【図１１】本発明を適用してなる単結晶製造装置の第５の実施形態の概略構成を育成過程におけるテーパ部形成時の状態で示すルツボ近傍の縦断面図である。
【図１２】本発明を適用してなる単結晶製造装置の第６の実施形態の概略構成と動作を示す縦断面図であり、単結晶のテーパ部の育成段階を示す図である。
【図１３】本発明を適用してなる単結晶製造装置の第６の実施形態の概略構成と動作を示す断面図であり、単結晶の直胴部の育成段階を示す図である。
【図１４】第６の実施形態の単結晶製造装置と従来の単結晶製造装置の側壁の高さ方向における発熱量の分布を比較した図である。
【図１５】第６の実施形態の単結晶製造装置と従来の単結晶製造装置の側壁の高さ方向における温度分布を比較した図である。
【図１６】従来の単結晶の製造装置におけるルツボ内の融液の対流の状態を示す図である。
【図１７】本発明を適用してなる単結晶製造装置の第７の実施形態の概略構成と動作を示す断面図であり、単結晶のテーパ部の育成段階を示す図である。
【図１８】第７の実施形態の単結晶製造装置と従来の単結晶製造装置の底の温度分布を比較した図である。
【図１９】本発明を適用してなる単結晶製造装置の第７の実施形態における変形例を示す断面図である。
【図２０】本発明を適用してなる単結晶製造装置の第７の実施形態における別の変形例を示す断面図である。
【符号の説明】
１　ルツボ
３　伝熱部材
７　放射熱遮断部材
１１　高周波コイル
１３　種結晶
１５　単結晶
１５ａ　テーパ部
１５ｂ　直胴部
１７　シードホルダー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for producing a single crystal used for, for example, electronic equipment and medical equipment.
[0002]
[Prior art]
There is known a single crystal manufacturing technique in which a single crystal is manufactured by bringing a seed crystal into contact with a melt of a heated raw material and pulling up the seed crystal. The growth of a single crystal is usually performed in the following procedure. A crucible provided with a heating means around the single crystal raw material is placed inside the furnace main body, and the crucible is heated by the heating means, and the raw material melt is heated by the crucible having a high temperature. When a seed crystal smaller in diameter than the single crystal to be produced is brought into contact with the surface of the melt, the melt that has come into contact with the seed crystal is radiated and cooled through the seed crystal, and the direction of the crystal of the seed crystal is reduced. The crystal is grown so as to be aligned. The seed crystal is pulled up in accordance with the growth of the crystal, and the grown crystal is sequentially cooled to further grow the crystal. This is repeated to produce a single crystal. In the initial stage of single crystal growth, in order to increase the diameter of the crystal, the seed crystal is pulled up, and a tapered portion whose diameter increases in a conical shape from the seed crystal is formed. When the diameter of the seed crystal reaches a predetermined size, the formation of the tapered portion that gradually enlarges the diameter is stopped, and the formation of a straight body in which the crystal grows in a columnar shape in the axial direction starts.
[0003]
At this time, since the liquid surface of the melt is located at a position lower than the upper end of the crucible, the single crystal to be pulled is heated by receiving radiant heat from the inner peripheral surface of the crucible while being below the upper end of the crucible, and is heated. The portion above the upper end emits heat and is cooled. After forming a straight body having a sufficient length, the straight body is separated from the melt, and the amount of heating of the crucible is gradually reduced to cool to room temperature.
[0004]
In such a single crystal manufacturing technique, when a defect or a crack occurs, a portion where the defect or the crack occurs becomes a defective portion and does not become a product. Therefore, it is necessary to reduce the occurrence rate of defective parts, that is, the defective rate, in order to improve productivity. One of the causes of generation of defects, cracks, and the like in a single crystal is a temperature distribution in the single crystal when the single crystal is grown or when the formed single crystal is cooled.
[0005]
As a technique for producing a single crystal in order to optimize the temperature distribution in the longitudinal direction, that is, the temperature gradient in the single crystal at the time of growing the single crystal or cooling the single crystal, a radiant heat reflecting plate is provided above the single crystal. It has been proposed to dispose the arrangement so as to suppress the heat dissipation above the single crystal and raise the radiant heat reflector together with the single crystal being pulled up (for example, see Patent Document 1). Further, it has been proposed to provide a movable fire-resistant lid at an upper opening of a furnace body containing a crucible in which a single crystal is generated (for example, see Patent Document 2). It has also been proposed to provide a lid on top of a crucible on which a single crystal is generated (for example, see Patent Document 3).
[0006]
On the other hand, natural convection caused by a density gradient caused by a temperature gradient of the melt in the crucible and Marangoli convection caused by a surface tension gradient are generated in the melt in the crucible. When convection of these melts occurs, the portion where the single crystal is grown, that is, the solid-liquid interface portion of the single crystal does not become flat, but becomes, for example, concave or convex, thereby forming a portion near the solid-liquid interface of the single crystal. The temperature distribution in the radial direction in the portion becomes non-uniform. As a single crystal manufacturing technique for reducing the non-uniformity of the temperature distribution in the vicinity of the solid-liquid interface of the single crystal, when pulling up the single crystal in order to make the shape of the solid-liquid interface part of the single crystal as flat as possible, By rotating a single crystal or rotating the central axis of a cylindrical crucible as a rotation axis, forced convection of the melt spreading in the radial direction of the crucible is generated, and the entire convection pattern of the melt is controlled. Has been proposed (for example, see Patent Document 4).
[0007]
[Patent Document 1]
JP-A-8-175896 (page 3-4, FIG. 5)
[Patent Document 2]
JP-A-6-157187 (page 2, FIG. 1)
[Patent Document 3]
JP 2001-316195 A (Pages 4-6, FIG. 1, FIG. 3)
[Patent Document 4]
JP-A-6-183877 (page 3-4, FIG. 1)
[0008]
[Problems to be solved by the invention]
Patent Document 1 aims to reduce the occurrence of defects and cracks by reducing the longitudinal temperature distribution in a single crystal during the process of growing the single crystal. However, if a radiant heat reflector is provided immediately above the single crystal, the difference in temperature distribution in the single crystal in the radial direction during cooling increases, so that it is difficult to reduce the occurrence of defects and cracks. Patent Literature 2 aims to reduce the cooling rate by covering the upper part of the refractory in the cooling process, reduce the temperature distribution in the single crystal, and reduce the occurrence of defects and cracks. However, no consideration has been given to the control of the surface temperature of the single crystal in the process of growing the single crystal, and the temperature distribution in the process of growing the single crystal cannot be adjusted properly. hard.
[0009]
In Patent Literature 3, since a lid is provided on the upper part of the crucible, the surface temperature of the single crystal above the crucible cannot be controlled in the cooling process, and the temperature distribution in the single crystal growing process is adjusted appropriately. And it is difficult to reduce the occurrence of defects and cracks. In addition, even in the early stage of the growth process of the single crystal, since the lid is provided on the upper portion of the crucible, the surface of the tapered portion of the single crystal, that is, the tapered surface rises in temperature, causing surface roughness, and conversely, defects and Cracks and the like may easily occur. As described above, with the single crystal manufacturing techniques of Patent Documents 1 to 3, the occurrence of defects and cracks may not be reduced in some cases, and it is difficult to reduce the defect rate.
[0010]
On the other hand, in high-frequency induction heating using high-frequency generation means including a high-frequency coil as a heating means, the amount of heat generated per unit volume per unit time is determined by the circumferential current J induced on the surface of the metal. Θ Is proportional to the square of And the closer the metal to the coil, the more J Θ Becomes larger. Further, the electromagnetic field has a property of being concentrated on the surface of the corner of the metal. Therefore, when a cylindrical crucible is heated by high-frequency induction heating, an electromagnetic field concentrates on an upper end portion of a side wall of the crucible and a peripheral portion of a bottom serving as a lower end portion. For this reason, the calorific value at the upper end portion and the lower end portion of the side wall of these crucibles is larger than at other portions. For this reason, for example, as the side wall becomes longer in the axial direction than the diameter of the bottom, the temperature of the portion other than the upper end portion and the lower end portion of the crucible side wall of the side wall becomes lower than the temperature of the upper end portion and the lower end portion. . Therefore, the temperature distribution of the crucible becomes non-uniform, and even when the seed crystal or the crucible is rotated as in Patent Document 4, the melt exhibits an undesirable convection pattern, and the solid-liquid interface of the single crystal becomes flat. May not be.
[0011]
Furthermore, even when the single crystal or crucible rotates as in Patent Document 4 to generate forced convection that spreads in the radial direction, the solid-liquid interface portion of the single crystal can be flattened, but the taper from the seed crystal. In the process of growing the portion, the outer diameter of the crystal is smaller than when the straight body portion of the single crystal is grown, so that forced convection spreading in the radial direction cannot be sufficiently generated. Therefore, depending on conditions such as the size of the bottom of the crucible, at the stage of growing the tapered portion from the seed crystal, the melt in the crucible exhibits an undesirable convection pattern, and the solid-liquid interface portion of the single crystal does not become flat. There are cases. As described above, even in the single crystal manufacturing technology of Patent Document 4, the solid-liquid interface portion of the single crystal is not flattened due to the conditions such as the size and shape of the crucible, and the temperature distribution is not uniform. May not be reduced, and it is difficult to reduce the defective rate.
[0012]
An object of the present invention is to reduce a defective rate in manufacturing a single crystal.
[0013]
[Means for Solving the Problems]
One of the main causes of defects and cracks in the crystal is that the temperature distribution in the single crystal becomes uneven because the outer periphery is cooled before the center of the single crystal in the cooling process It is in. In particular, the inventors of the present invention have found that the thermal stress due to the linear temperature distribution in the longitudinal direction of the single crystal is small as compared with the large influence of the thermal stress due to the temperature difference in the radial direction of the single crystal. . From this fact, it is effective to reduce the temperature difference in the radial direction of the single crystal by keeping the outer peripheral surface of the crystal in the cooling process, and further, it is possible to reduce the temperature difference in the radial direction of the single crystal, The inventors of the present invention have found that it is effective to cool only the upper end surface of the crystal, that is, the tapered surface of the tapered portion to linearize the temperature distribution in the longitudinal direction and maintain the cooling rate.
[0014]
Therefore, an apparatus for producing a single crystal according to the present invention includes a crucible containing a raw material, a heating means for heating the raw material in the crucible, and a crystal moving means for moving a seed crystal upward from the crucible. A crystal manufacturing apparatus, comprising a heat transfer member extending upward from at least the vicinity of an upper end portion of a side wall of the crucible, surrounding a formed single crystal, and provided with a heat transfer member formed of a material having heat conductivity. Solution to the Problems
[0015]
With this configuration, when the single crystal coming out of the crucible is cooled, the heat of the crucible below the single crystal is transmitted to the outside of the crucible by the heat transfer member, and the heat is released from the outer peripheral surface of the single crystal. Reduce the amount of heat. Therefore, the temperature difference in the radial direction of the single crystal is reduced. Therefore, the occurrence of defects and cracks can be reduced, and the defect rate can be reduced.
[0016]
Further, the apparatus for producing a single crystal of the present invention has a taper portion that gradually increases in diameter continuously with a seed crystal of a formed single crystal and a taper portion of a formed single crystal at least during cooling after growing a single crystal. The above problem is solved by providing a configuration in which a radiant heat shield that blocks upward radiant heat from a boundary portion with the cylindrical straight body portion is provided.
[0017]
In this way, when the straight body of the single crystal that has come out of the crucible is cooled, heat radiation due to radiative heat transfer from the outer peripheral surface of the straight body of the single crystal to the upper part is cut off, and relatively relatively from above the apparatus. The low-temperature gas is prevented from flowing around the outer peripheral surface of the single crystal straight body. For this reason, the temperature difference in the radial direction in the straight body portion of the single crystal is reduced. Further, only the tapered surface of the tapered portion of the single crystal is cooled to linearize the temperature distribution in the longitudinal direction, and the cooling rate can be maintained. Therefore, the occurrence of defects and cracks can be reduced, and the defect rate can be reduced.
[0018]
Further, a radiant heat shield that blocks upward radiant heat from the boundary between the tapered portion and the straight body can be moved in the vertical direction, and a radiant heat shield that moves the radiant heat shield in the vertical direction. A configuration in which a body moving unit is provided is adopted. With such a configuration, even when growing a single crystal, the radiant heat shield is positioned at the boundary between the tapered portion and the straight body, and radiant heat upward from the boundary between the tapered portion and the straight body. Can be cut off, the occurrence of defects and cracks can be further reduced, and the defect rate can be further reduced.
[0019]
In addition, the inventors of the present invention have found that another cause of the occurrence of defects or cracks generated in the crystal is that the temperature of the tapered surface of the tapered portion rises excessively during the growth of the single crystal and surface roughness occurs. I found it. In the initial stage of the growth of the single crystal, when forming the tapered portion where the tapered portion of the single crystal is located in the crucible, suppressing the temperature rise of the tapered surface of the tapered portion suppresses the surface roughness of the tapered surface. It is effective to do. On the other hand, after the formation of the single-crystal tapered portion, when forming the single-crystal straight body, heat radiation from the tapered portion coming out of the crucible is increased, and from the outer peripheral surface of the straight body in the crucible. Is effective in reducing the nonuniformity of the temperature distribution in the radial direction of the single crystal being formed, that is, the temperature difference at the liquid surface position of the melt, that is, at the solid-liquid interface position.
[0020]
Therefore, a method for producing a single crystal according to the present invention is a method for producing a single crystal, in which a crucible containing a raw material is heated and pulled up while bringing a seed crystal into contact with a melt of the raw material to produce a single crystal. When forming the tapered portion of the single crystal in the initial stage of the growth of the single crystal in which the diameter of the single crystal is increased, and when forming the tapered portion of the single crystal during the formation of the single-crystal straight body portion that grows in a cylindrical shape continuously from the tapered portion, the crucible is used. The above problem is solved by blocking the radiant heat reaching the tapered portion of the single crystal from the inner surface of the substrate.
[0021]
Further, the apparatus for producing a single crystal of the present invention includes a radiant heat shield in a crucible that surrounds the single crystal and blocks radiant heat from an inner surface of the crucible toward a single crystal located in the crucible; And a radiant heat shield moving means for moving the crucible in the vertical direction. The radiant heat shield in the crucible is moved to a position surrounding the tapered part of the crystal, and the radiant heat shield in the crucible is separated from the single crystal at the position away from the single crystal during the formation of a single-crystal straight body that grows in a cylindrical shape continuously to the tapered part. The above problem is solved by adopting a configuration in which the body is moved.
[0022]
With such a configuration, when the single crystal tapered portion is formed, heating of the tapered surface of the tapered portion by radiant heat from the inner surface of the crucible is suppressed by the radiant heat shield in the crucible, and a rise in the temperature of the tapered surface is suppressed. The surface roughness of the tapered surface can be suppressed. On the other hand, when the single-crystal straight body is formed, the radiant heat shield in the crucible moves to a position away from the crystal, so that heat radiation upward from the tapered portion of the single crystal is not hindered, and the single-crystal located in the crucible is not hindered. The outer peripheral surface of the straight body of the crystal receives the radiant heat from the inner surface of the crucible, so that the temperature drop of the outer periphery of the single body of the single crystal is reduced, and the single crystal at the crystal growth surface, that is, at the liquid level position of the melt Can be reduced in the radial direction. Therefore, the occurrence of defects and cracks can be reduced, and the defect rate can be reduced.
[0023]
Further, the heating means is a high-frequency generating means including a high-frequency coil which is wound around the crucible with the axis vertical and energized by a high-frequency current, surrounds the single crystal, and is located inside the crucible from the inner surface of the crucible. The radiant heat shield in the crucible that blocks radiant heat toward the single crystal is made of a non-metallic material, and has a central cone that has a seed crystal and an opening through which a rod-shaped or band-shaped seed holder for crystal moving means can be inserted. It is desirable to adopt a configuration in which the shape or the inner diameter is a cylindrical shape larger than the diameter of the straight body portion of the single crystal.
[0024]
Furthermore, the method for producing a single crystal according to the present invention is characterized in that the single crystal grows in a cylindrical shape continuously at the time of forming the taper portion of the single crystal at the initial stage of growth of the single crystal and increasing the diameter of the single crystal and continuously growing at the taper portion. During the formation, when the single crystal is formed in the straight body, the above problem is solved by blocking the radiant heat upward from the upper end of the crucible.
[0025]
In addition, the single crystal manufacturing apparatus of the present invention includes a straight body radiant heat shield that allows a single crystal to pass therethrough and blocks radiant heat upward from the upper end portion of the crucible, and vertically moves the straight body radiant heat shield. And a heating means for heating a portion below the upper end of the crucible, wherein the straight-body radiation heat-shielding body moving means moves the single-crystal growth initial stage. However, when forming the tapered portion of the single crystal to increase the diameter of the single crystal, the straight body radiant heat shield is moved to a position away from the upper end portion of the crucible, and the single crystal grows in a columnar shape continuously to the tapered portion. At the time of forming the straight body part, the straight body part radiant heat shield is placed between the outer circumferential surface of the single crystal straight body and the inner circumferential surface of the crucible, or the outer circumferential surface of the single crystal straight body and the upper end part of the crucible. The above-mentioned problem is solved by adopting a configuration in which it is located between them.
[0026]
With this configuration, when the single-crystal straight body is formed, the heat radiation from the outer peripheral surface of the single-crystal straight body in the crucible is reduced by the straight-body heat radiation blocker. The temperature difference in the radial direction of the single crystal at the surface, that is, at the liquid surface position of the melt can be reduced. On the other hand, when forming the taper portion of the single crystal, since there is nothing to hinder heat radiation from the taper surface of the taper portion, heat can be radiated upward from the taper portion, and the heating amount of the portion above the crucible melt surface is reduced. By reducing the temperature, the rise in temperature of the tapered surface can be suppressed, and the surface roughness can be suppressed. Therefore, the occurrence of defects and cracks can be reduced, and the defect rate can be reduced.
[0027]
Further, the heating means is a high-frequency generating means including a high-frequency coil wound around the crucible with the axis vertical and energized by a high-frequency current, and a single crystal can be inserted therethrough, and radiant heat upward from the upper end portion of the crucible is provided. If the radiant heat shield that cuts off is made of metal, the heat radiation from the outer periphery of the single crystal straight body is further reduced, and the single crystal generation surface, that is, the single crystal at the liquid level position of the melt The temperature difference in the radial direction can be further reduced.
[0028]
Further, the apparatus for producing a single crystal according to the present invention moves the crucible upward from inside the crucible while rotating the seed crystal, and a high-frequency generating means including a high-frequency coil provided around the crucible. An apparatus for producing a single crystal comprising crystal moving means, wherein a portion between an upper end portion and a lower end portion of a side wall of a crucible is provided with a wall-side heating member for heating by operation of high-frequency generating means. Solves the above problem.
[0029]
With such a configuration, when the wall-side heating member is provided, in addition to the upper end portion and the lower end portion of the crucible, a portion between the upper end portion and the lower end portion of the crucible is also heated, and the crucible is heated. The temperature distribution on the side wall can be made uniform. As a result, convection of the melt rising toward the liquid surface along the side wall of the crucible can be generated, and it is possible to prevent the melt in the crucible from exhibiting an undesirable convection pattern. Therefore, regardless of conditions such as the size and shape of the crucible, the solid-liquid interface portion of the single crystal can be flattened to reduce the occurrence of defects and cracks, thereby reducing the defective rate.
[0030]
Further, the apparatus for producing a single crystal according to the present invention solves the above-mentioned problem by adopting a configuration in which a bottom-side heating member that heats a central portion of the bottom of the crucible by operating a high-frequency generating means is provided on the bottom of the crucible.
[0031]
With such a configuration, when the bottom-side heating member is provided, in addition to the lower end portion of the crucible, that is, the center portion of the bottom, in addition to the peripheral portion of the bottom of the crucible, the center of the bottom of the crucible is heated. The convection of the melt which rises from the portion toward the solid-liquid interface portion of the seed crystal or the single crystal and spreads in the radial direction on the solid-liquid interface portion of the seed crystal or the single crystal can be generated, and the melt in the crucible is formed. Undesirable convection patterns can be prevented. Therefore, regardless of conditions such as the size and shape of the crucible, the solid-liquid interface portion of the single crystal can be flattened to reduce the occurrence of defects and cracks, thereby reducing the defective rate.
[0032]
Further, the wall-side heating member is formed in a portion between the upper end portion and the lower end portion of the outer surface of the crucible side wall, and is provided with a projecting shape provided by extending along the circumferential direction of the outer surface of the crucible side wall with a conductive material. It is configured to be formed of members. With such a configuration, the electromagnetic field generated by the high-frequency coil concentrates on a sharp corner close to the high-frequency coil. The wall-side heating member formed by the protruding member also generates heat, and can heat a portion between the upper end portion and the lower end portion of the crucible.
[0033]
Further, the bottom-side heating member has a heat-transfer portion formed of a material having thermal conductivity that transmits heat to the central portion of the bottom outer surface of the crucible, and a material having a larger diameter than the heat-transfer portion and having conductivity. And a plate-like heat-generating portion formed by the above. Further, the heating member has a heat insulating member formed of a heat insulating material having a through hole serving as a heat transfer portion at a position corresponding to the center portion of the bottom outer surface of the crucible, and a diameter larger than the through hole of the heat insulating member. And a plate-like heat generating portion formed of a conductive material. With such a configuration, the electromagnetic field generated by the high-frequency coil concentrates on a sharp corner close to the high-frequency coil. Fever. Since the heat of the heat generating portion is transmitted to the central portion of the bottom of the crucible through the heat transfer portion of the bottom heating member or the through hole of the heat insulating member, the central portion of the bottom of the crucible can be heated.
[0034]
Furthermore, if the heat generating portion has a disk shape and the diameter of the heat generating portion is equal to or more than 2/3 of the diameter of the bottom of the crucible, the high frequency generating means can surely generate heat at the peripheral portion of the heat generating portion.
[0035]
Further, the wall-side heating member and the bottom-side heating member are detachably attached to the crucible. Furthermore, the wall side heating member and the bottom side heating member move the wall side heating member and the bottom side heating member between a position where the wall side heating member and the bottom side heating member are in contact with the crucible and a position where the wall side heating member and the bottom side heating member are separated from the crucible. A configuration is provided in which a heating member moving unit is provided. With such a configuration, the wall-side heating member and the bottom-side heating member are attached to and detached from the crucible in accordance with, for example, the stage of growing a single crystal, and the side wall and the bottom wall-side heating unit and the bottom-side heating unit of the crucible are used. Heating can be selected as required.
[0036]
Further, when growing a single crystal using a single crystal manufacturing apparatus having a high frequency generating means including a high frequency coil and a crystal moving means moving upward from inside the crucible while rotating the seed crystal, a side wall of the crucible is grown. If the method for growing a single crystal is to heat at least one of the portion between the upper end portion and the lower end portion and the central portion at the bottom of the crucible, the heating distribution of the melt in the crucible can be controlled, so that the single crystal to be grown Quality can be improved.
[0037]
The quality of a single crystal can be improved by using a single crystal manufactured by any one of the above-described apparatus for manufacturing a single crystal or a method for manufacturing a single crystal.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a first embodiment of a single crystal manufacturing technique according to the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a cooling process. FIG. 2 is a longitudinal sectional view showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a growing process.
[0039]
The apparatus for producing a single crystal according to the present embodiment is, for example, a apparatus for producing a single crystal having a melting point of 1500 ° C. or more. As shown in FIGS. 1 and 2, a cylindrical crucible 1 surrounds an outer surface of a side wall 1 a of the crucible 1. A cylindrical heat transfer member 3 having a height higher than the crucible 1; a radiant heat shield member provided at an upper end portion of the heat transfer member 3 and serving as a disc-shaped boundary portion radiant heat shield having an opening 5 in a central portion; 7, a refractory 9 surrounding the outside of the heat transfer member 3, high-frequency generating means including a high-frequency coil 11 for generating a high frequency outside the refractory 9, and a rod-shaped or band-shaped holding the seed crystal 13 and the grown single crystal 15. And a crystal moving means for pulling up the crystal held by the seed holder 17 while rotating the crystal holder.
[0040]
The crucible 1 is a cylindrical container having an upper end opened and a lower end closed to form a bottom 1b. The crucible 1 is made of a conductive and high-melting metal material such as iridium, platinum, tungsten, molybdenum, or the like. ing. The heat transfer member 3 is formed of a material having heat conductivity, for example, high heat conductive alumina, ceramic, iridium, or the like. The heat transfer member 3 has a cylindrical shape whose upper end and lower end are opened and whose inner diameter is the same as the outer diameter of the crucible 1 or larger than the outer diameter of the crucible 1. It is installed in an enclosed state. When the single crystal 15 is held during the cooling process of manufacturing the single crystal as shown in FIG. It is located at a position corresponding to a boundary with a cylindrical straight body 15b formed continuously with the portion 15a.
[0041]
The radiant heat shield member 7 serving as a boundary portion radiant heat shield has a disk shape or a flat ring shape having an opening having a diameter larger than the diameter of the straight body portion 15b of the single crystal 15 at the center portion, and radiant heat is prevented. It is formed of a material that can be shut off, for example, iridium, alumina, ceramic, zirconia, or the like. The radiation heat blocking member 7 is located at a position corresponding to the upper end of the heat transfer member 3, that is, at a position corresponding to the boundary between the tapered portion 15 a of the single crystal 15 and the straight body 15 b held in the cooling process of manufacturing the single crystal. In addition, an outer peripheral edge portion is attached to and held by the refractory 9. It is desirable that the opening provided in the central portion of the radiation heat shielding member 7 be formed with a diameter as small as possible so as not to contact the single crystal 15. The material forming the radiant heat blocking member 7 may be a heat conductive material or a heat insulating material as long as it can block radiant heat. It is more desirable to use a heat-insulating material for this purpose.
[0042]
The refractory 9 is a cylindrical container larger than the crucible 1 and the heat transfer member 3 having an open upper end and a closed lower end to form a bottom, and is a high-temperature resistant material having insulating and heat insulating properties, for example. It is made of low thermal conductive alumina, zirconia, alumina wool, or the like. The height of the refractory 9 is higher than the heat transfer member 3. The high-frequency generating means includes a high-frequency power supply not shown in FIGS. 1 and 2, a high-frequency coil 11 electrically connected to the high-frequency power supply by wiring (not shown), and the like. The high-frequency coil 11 is installed outside the refractory 9 at a position corresponding to the side wall 1a of the crucible 1 so as to surround the refractory 9 with the vertical axis as the center axis. The crystal moving means includes a rod-shaped or band-shaped seed holder 17, and a drive unit (not shown) for hanging the seed holder 17 while rotating the seed holder 17.
[0043]
The crucible 1, the heat transfer member 3, the radiant heat blocking member 7, the refractory 9, the high-frequency coil 11, and a part of the seed holder 17 are housed in a container 19. The crucible 1 is supported on a support member 21 installed on the bottom of the container 19. A through hole 23 is formed in the ceiling of the container 19 at a position corresponding to the center of the opening of the crucible 1, and the seed holder 17 is inserted into the through hole 23 in a state of being suspended from above. .
[0044]
The operation of the apparatus for manufacturing a single crystal having such a configuration and the features of the present invention will be described. The crucible 1 contains a crystal material that is a crystal raw material, for example, Gd. 2 SiO 5 , Bi 4 Ge 3 O 12 , Lu 2 SiO 5 And the like are accommodated, and a melt 25 is formed. When a high-frequency current flows from a high-frequency power supply (not shown) to the high-frequency coil 11, an induced current flows through the conductive crucible 1. Thereby, the crucible 1 is heated by the Joule heating, and the melt 25 in the crucible 1 that has been heated is brought into a heated state. In this state, when the seed crystal 13 held at the lower end of the seed holder 17 is brought into contact with the melt 25 and pulled up from the melt 25, a single crystal 15 is generated as shown in FIG. In the production of the single crystal, as shown in FIG. 2, first, the tapered portion 15a of the single crystal 15 is formed in a conical shape having a diameter gradually increasing continuously from the seed crystal 13, and the columnar shape is formed continuously from the tapered portion 15a. 1 and a cooling step of leaving the generated single crystal 15 pulled up and holding it in the seed holder 17 to cool it, as shown in FIG.
[0045]
In the growth process as shown in FIG. 2, the single crystal 15 to be grown is radiated from the surfaces of the seed crystal 13 and the single crystal 15 toward the ceiling of the container 19 by radiant heat transfer. Since the temperature of the single crystal 15 is lower than the melting point of the crystal material by being cooled by the heat conduction through 17, the lower surface of the single crystal 15 in contact with the melt 25 becomes a growth surface 15c, and a new crystal grows.
[0046]
At this time, the heat generated by the crucible 1 is generated in both the portion in contact with the melt 25 and the portion above the melt 25, but the heat generated by the heat generated by the crucible 1 causes the heat transfer member 3 to generate heat. It is conducted and transmitted above the crucible 1. For this reason, the space surrounded by the heat transfer member 3 has a temperature close to the single crystal 15 immediately after generation at any height as compared with the case where the heat transfer member 3 is inside. Therefore, in the growing process, heat radiation due to radiant heat transfer from the outer peripheral surface of the single crystal 15 which is raised upward from the crucible 1 and is cooled to the space around the single crystal 15 outside the crucible 1 is reduced, and the radial direction of the single crystal 15 is reduced. Is reduced.
[0047]
On the other hand, in the cooling process, as shown in FIG. 1, the long-grown single crystal 15 is separated from the melt 25, and the heating amount is gradually reduced to cool to room temperature. In this cooling process, the single crystal 15 that has grown sufficiently long moves upward and is separated from the melt 25. The temperature is lowered by gradually reducing the high-frequency power generated from the high-frequency coil 11. At this time, similarly to the growing process, the heat generated by the heat generated by the crucible 1 is transmitted to the heat transfer member 3, so that heat radiation from the outer peripheral surface of the single crystal 15 to the space around the single crystal 15 outside the crucible 1 is reduced.
[0048]
Further, in the cooling process, the radiant heat shield 7 is located at a position corresponding to the boundary between the tapered portion 15a and the straight body portion 15b of the single crystal 15, so that the radiant heat shield 7 serves as a lid, The heat radiation due to radiative heat transfer from the boundary between the tapered portion 15a and the straight body portion 15b of the crystal 15 is reduced. Relatively low-temperature gas, such as a ceiling portion in the container 19, is less likely to flow downward from the boundary between the tapered portion 15a of the single crystal 15 and the straight body portion 15b. That is, only the straight body 15b of the single crystal 15 is kept warm, and heat radiation from only the straight body 15b of the single crystal 15 is reduced. Thereby, the temperature difference in the radial direction of straight body portion 15b of single crystal 15 is reduced.
[0049]
Generally, in the cooling process, unlike the growing process, the heat generation of the crucible 1 is small, so that a temperature difference in the radial direction of the single crystal 15, that is, an uneven temperature distribution is likely to occur. However, in the present embodiment, the actions of both the heat transfer member 3 and the radiation heat shield 7 are combined, so that heat radiation from the outer peripheral surface of the straight body 15b of the single crystal 15 during the cooling process is reduced, and the temperature difference in the radial direction is reduced. Is reduced. Further, in the tapered portion 15a of the single crystal 15, the radiant heat transfer from the tapered surface of the tapered portion 15a and the convective heat transfer due to the relatively low temperature gas in the container 19 flowing on the tapered surface of the tapered portion 15a. There is heat radiation, and the single crystal 15 can be cooled at an appropriate cooling rate. Due to heat radiation from the tapered surface of the tapered portion 15a, a temperature gradient is generated in the longitudinal direction of the single crystal 15, that is, in the longitudinal direction, with a constant linear temperature distribution. Is small, defects and cracks are unlikely to occur due to the temperature difference in the longitudinal direction.
[0050]
As described above, in the single crystal manufacturing apparatus and the single crystal manufacturing method of the present embodiment, the heat transfer member 3 is provided, and when the single crystal 15 coming out of the crucible 1 is cooled, the heat of the crucible 1 is transferred. The heat is transmitted to the space surrounded by the heat transfer member 3 above the crucible 1 by the heat member 3 and the amount of heat radiation from the outer peripheral surface of the single crystal 15 is reduced. Therefore, the temperature difference in the radial direction of single crystal 15 is reduced. Therefore, the occurrence of defects, cracks, and the like can be reduced, and the defect rate in the production of a single crystal can be reduced.
[0051]
Further, in the single crystal manufacturing apparatus and the single crystal manufacturing method of the present embodiment, the radiant heat shield 7 that blocks upward radiant heat from the boundary between the tapered portion 15a and the straight body portion 15b of the single crystal 15 is provided. Therefore, when the single crystal 15 is cooled in the cooling process, heat radiation due to radiant heat transfer from the outer peripheral surface of the straight body portion 15b of the single crystal 15 is shut off, and the single crystal 15 is relatively removed from the vicinity of the ceiling in the container 19 or the like. The flow of the low-temperature gas into the space around the outer peripheral surface of the straight body 15b of the single crystal 15 is blocked. For this reason, the temperature difference in the radial direction in the straight body portion 15b of the single crystal 15 is reduced. Further, only the tapered surface of the tapered portion 15a of the single crystal 15 is cooled to make the temperature distribution in the longitudinal direction of the single crystal 15 linear, thereby maintaining the cooling rate. Therefore, the occurrence of defects, cracks, and the like can be reduced, and the defect rate in the production of a single crystal can be reduced.
[0052]
In addition, in the single crystal manufacturing apparatus and the single crystal manufacturing method of the present embodiment, since the heat transfer member 3 is provided together with the radiant heat shield 7, the heat retaining effect of the straight body 15b of the single crystal 15 in the cooling process. Can be improved, the occurrence of defects and cracks can be further reduced, and the defect rate in the production of a single crystal can be further reduced.
[0053]
Furthermore, the fact that the occurrence of defects and cracks can be further reduced means that the loss of crystals leading to defects and cracks can be reduced, and the loss of single crystal crystals that have become products can also be reduced. The quality of the single crystal can also be improved.
[0054]
By the way, in the conventional single crystal manufacturing technology, a radiant heat reflector is provided immediately above the single crystal, a refractory upper part is covered in a cooling process, or a lid is provided above a crucible. For this reason, the cooling time in the growing process and the cooling process becomes longer, the growth rate of the single crystal in the growing process decreases, and the cooling time of the single crystal in the cooling process becomes longer, so that the production capacity decreases. There are also problems.
[0055]
In contrast, in the single crystal manufacturing technique of the present embodiment, in the growing process, there is no lid, and in the cooling process, heat can be radiated from the tapered portion of the single crystal. The growth rate of the single crystal does not easily decrease, and the cooling time in the cooling process does not easily increase. Therefore, a decrease in production capacity can be suppressed.
[0056]
Further, in the present embodiment, the disk-shaped radiant heat shield member 7 provided at the upper end portion of the heat transfer member 3 and having the opening 5 at the center is shown as the boundary portion radiant heat shield. The blocker is not limited to such a configuration, and various configurations can be employed as long as it is located at a position corresponding to a boundary between the straight body portion and the tapered portion of the single crystal and can block upward radiant heat. For example, as shown in FIG. 3, the upper end of the refractory 9 is located at a position corresponding to the boundary between the tapered portion 15 a and the straight body 15 b of the single crystal 15 in the cooling process. A lid 9a protruding in a ring shape from the upper end toward the single crystal may be formed as a boundary portion radiation heat shield.
[0057]
At this time, since the refractory 9 is thick, the lower surface of the lid 9a of the refractory 9 is positioned at a position corresponding to the boundary between the tapered portion 15a of the single crystal 15 and the straight body 15b. The opening 9b formed in the center of 9a is a tapered opening whose diameter gradually increases as it goes upward. Thus, radiant heat upward from the boundary between the tapered portion 15a of the single crystal 15 and the straight body portion 15b is shut off, and the tapered portion 15a of the single crystal 15 is covered by the thick refractory 9 lid 9a. It can be prevented from being surrounded and kept warm.
[0058]
Further, in the present embodiment, as the heat transfer member, the cylindrical heat transfer member 3 surrounding the outer surface of the side wall 1a of the crucible 1 and having a height higher than the crucible 1 is shown. The present invention is not limited to this, and various configurations can be adopted as long as the heat in the vicinity of the crucible 1 or the crucible 1 can be transmitted upward. For example, as shown in FIG. 3, the lower end portion may be located near the upper end portion of the crucible 1, and the upper end portion may be set to a height halfway of the straight body 15 b of the single crystal 15 in the cooling process. Thus, the heat transfer member does not need to be in contact with the crucible 1 or surround the crucible 1, and the height can be appropriately selected depending on conditions such as whether or not the boundary portion radiant heat shield is provided.
[0059]
Further, in the present embodiment, the configuration in which both the radiant heat blocking member 7 and the heat transfer member 3 serving as the boundary portion radiant heat blocker are provided, but either the boundary portion radiant heat blocker or the heat transfer member is provided. Even if only one is provided, the effect of the present invention can be obtained. Here, an example in which the effect obtained when only the boundary portion radiant heat shield is provided is calculated by numerical simulation. As a calculation condition, the crystal material is Gd having a melting point of 1950 ° C. 2 SiO 5 The temperature distribution in the crystal was calculated with and without the radiation heat shielding member 7 as shown in FIG. As a result of the calculation, the temperature difference in the radial direction at the height of the central portion of the single crystal 15 in the cooling process is about 50 ° C. in the case where the radiant heat shield 7 is not provided, whereas the radiant heat shield 7 is provided. In this case, the temperature was about 35 ° C. Thus, even if only the boundary part radiant heat shield is provided, the temperature difference in the radial direction of the single crystal in the cooling process can be reduced, cracking due to thermal stress, etc. can be prevented, the defect rate can be reduced, and the quality can be improved. It becomes possible. However, if both the boundary part radiant heat shield and the heat transfer member are provided, these effects can be improved as compared with the case where either one is provided.
[0060]
(Second embodiment)
Hereinafter, a second embodiment of a single crystal manufacturing technique according to the present invention will be described with reference to FIG. FIG. 4 is a longitudinal sectional view showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a growth process. In the present embodiment, the same components and operations as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The configuration and features different from those in the first embodiment will be described.
[0061]
The difference between the single crystal manufacturing technique of the present embodiment and the first embodiment is that the boundary portion radiant heat shield can be moved in the vertical direction. That is, as shown in FIG. 4, the single crystal manufacturing apparatus according to the present embodiment has a disk ring-shaped radiant heat shield in which a through hole 27 corresponding to the diameter of the straight body portion 15b of the single crystal 15 is formed in the central portion. A member 29, a radiant heat shield moving means for supporting the radiant heat shield member 29 and moving the radiant heat shield member 29 in the vertical direction are provided. The radiant heat shielding member 29 serving as the boundary part radiant heat shield is supported by a rod-shaped support member constituting the boundary part radiant heat shield moving means with the surface of the disk facing up and down. The boundary portion radiant heat shield moving means supports the radiant heat shield member 29, is inserted into a through-hole formed in the ceiling of the container 19, and extends in a vertical direction, and extends outside the container 19. A moving mechanism (not shown) for moving the supporting member 31 in the vertical direction is provided.
[0062]
In this embodiment, the radiant heat shielding member 29 is located at a position corresponding to the boundary between the tapered portion 15a and the straight body portion 15b of the single crystal 15 not only in the cooling process but also in the growing process. It moves upward as the crystal 15 grows. As a result, in both the growing process and the cooling process, the temperature difference in the radial direction of the single crystal 15 is reduced by the action of the radiation heat blocking member 29, and the defective rate in the production of the single crystal can be reduced.
[0063]
Further, effects such as improvement of quality and improvement of production capacity can be obtained.
[0064]
Depending on conditions such as the type of single crystal to be manufactured, the radiant heat shielding member 29 is moved to the upper part of the apparatus away from the single crystal 15 or the refractory 9 during the growing process, and is moved to the boundary of the single crystal 15 only during the cooling process. An operation of positioning can also be performed. In this case, since there is no radiant heat shielding effect by the radiant heat blocking member 29 in the growing process, the growth rate can be increased by radiating heat from the periphery of the single crystal 15, and the temperature distribution in the radial direction of the single crystal 15 can be reduced only in the cooling process. It is made uniform. Depending on conditions such as the type of single crystal to be manufactured, a temperature difference in the radial direction of the crystal occurs in the process of growing the single crystal 15, but when the material properties of the crystal are close to the melting point, there is fluidity and defects and cracks are generated. In some cases, it is unlikely to occur.
[0065]
(Third embodiment)
Hereinafter, a third embodiment of a single crystal manufacturing technique according to the present invention will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a state where a tapered portion is formed in a growing process. FIG. 6 is a perspective view of the vicinity of the crucible shown so that the arrangement of the radiant heat shielding cylinder when forming the tapered portion of the single crystal can be understood. FIG. 7 is a longitudinal sectional view showing a state when a straight body is formed in the process of growing the single crystal manufacturing apparatus shown in FIG. Note that, in the present embodiment, the same components and operations as those in the first and second embodiments are denoted by the same reference numerals.
[0066]
As shown in FIG. 5, the apparatus for manufacturing a single crystal according to the present embodiment includes a cylindrical container 19 having a rectangular vertical section, and a support member 21 provided on the bottom surface 19a of the container 19. Refractory 9 which is a cylindrical heat insulating material supported concentrically with container 19, crucible 1 disposed concentrically with refractory 9 on bottom surface 9 a of refractory 9, and upper surface of container 19 A crystal moving means including a rod-shaped and band-shaped seed holder 17 which is inserted through an opening formed in the center portion of the refractory 9 b and is arranged to be able to move up and down on the center line of the refractory 9, and is attached to a lower end of the seed holder 17. A seed crystal 13, a radiant heat blocking cylinder 33 that is arranged concentrically with the rod-shaped or band-shaped seed holder 17 and that is configured to be able to move up and down along the center line of the refractory 9 and that serves as a radiant heat shield in a crucible; Formed on the upper surface 19b of the container 19 A radiant heat shutoff cylinder moving means which is inserted into the opening and moves the radiant heat shutoff cylinder 33 up and down along the center line of the refractory 9; It comprises an object 9 and a high-frequency coil 11 for high-frequency induction heating of the crucible 1 wound concentrically.
[0067]
The container 19 has a cylindrical shape whose upper and lower sides are closed, and an opening through which the seed holder 17 is inserted into the upper surface 19b, and a support member 35 of a rod-shaped radiant heat blocking cylinder 33 included in the radiant heat blocking cylinder moving means is inserted. Openings are formed. The refractory 9 has a cylindrical shape with the lower end closed at the bottom surface 9a and the upper part opened. The high-frequency coil 11 is wound from the lower end of the refractory 9 to a position above the outer peripheral surface position of the refractory 9 corresponding to the upper end of the crucible 1 so as to heat the entire crucible 1. Have been. The crucible 1 is filled with a melt 25 as a single crystal material to such an extent that the liquid surface comes to a position slightly lower than the upper end of the crucible 1.
[0068]
The radiation heat shielding cylinder 33 is made of a nonmetallic material, for example, the same material as the crystal material, and has a short cylindrical shape having an inner diameter equal to or larger than the diameter of the straight body of the product single crystal as shown in FIG. Has made. The crystal moving means includes a seed holder 17 and a moving mechanism (not shown) for moving the seed holder 17 in the vertical direction. Similarly, the radiant heat shield moving means in the crucible includes a support member 35, a moving mechanism (not shown) for moving the support member 35 in the vertical direction, and the like.
[0069]
The operation of the apparatus for manufacturing a single crystal having such a configuration and the features of the present invention will be described. A high frequency is generated in the vicinity of the crucible 1 by energizing the high-frequency coil 11, and the metal crucible 1 generates heat. The temperature of the crucible 1 becomes high, and the melt 25 of the crystal material becomes high. The lower end of seed crystal 13 is brought into contact with melt 25, and melt 25 in contact with seed crystal 13 is cooled by heat conduction through seed crystal 13 and seed holder 17, so that seed crystal 13 has a temperature equal to or lower than the melting point of the crystal material. Therefore, a new crystal, that is, a single crystal 15 grows on the surface of the seed crystal 13 in contact with the melt 25. As the new crystal grows, the seed crystal 13 is pulled upward by the seed holder 17. The seed crystal 13 radiates heat from the surfaces of the seed crystal 13 and the single crystal 15 to the ceiling of the vessel 19 and the inner surface of the refractory 9, and the seed crystal 13 is radiated. Since the single crystal 15 is cooled by the heat conduction through the crystal 13 and the seed holder 17 and is lower than the melting point of the crystal material, a new crystal grows on the surface of the single crystal 15 in contact with the melt 25.
[0070]
At the time of forming the tapered portion at the initial stage of the growth of the single crystal, as shown in FIG. 5, the upper surface of the single crystal 15 has a tapered portion 15a having a conical divergent tapered shape so as to gradually increase the diameter of the single crystal 15. It is formed. At this stage, the tapered portion 15a is located between the crucible inner surface 37 and the tapered portion 15a of the single crystal 15 so that the tapered surface of the taper portion 15a does not directly face the crucible inner surface 37 above the liquid surface of the melt 25. At the position, the radiation heat shielding cylinder 33 is moved and arranged concentrically with the seed crystal 13, that is, the seed holder 17. The axial length of the radiation heat blocking cylinder 33 is from the uppermost portion of the tapered surface of the tapered portion 15a to the lowermost portion of the tapered surface of the tapered portion 15a even when the liquid level of the melt 25 is the lowest when the tapered portion is formed. The length is set such that radiant heat from the crucible inner surface 37 can be prevented from reaching the tapered surface of the tapered portion 15a.
[0071]
The heat generated by the crucible 1 is generated in both the portion in contact with the melt 25 and the portion above the melt 25. However, when the tapered portion shown in FIG. Radiation heat to the tapered surface of the tapered portion 15a is cut off, so that the temperature of the tapered surface of the tapered portion 15a can be kept low, and surface roughness due to thermal etching of the tapered surface does not occur. Since the radiation heat blocking cylinder 33 is made of a nonmetallic material, it is not heated by high frequency.
[0072]
When the diameter of the single crystal 15 increases and reaches a predetermined size, as shown in FIG. 7, the formation of the tapered portion 15a ends, and the process shifts to forming a straight body. In the formation of the straight body portion, the single crystal 15 is grown long in a columnar shape, and the straight body portion 15b is formed. At this time, the radiation heat shielding cylinder 33 moves away from the crucible 1 and the single crystal 15 to the upper part of the container 19, and the outer peripheral surface of the straight body 15 b of the single crystal 15 directly faces the crucible inner surface 37.
[0073]
When the process shifts to the formation of the straight body portion, as shown in FIG. 7, the radiation heat shielding cylinder 33 is moved upward, so that the outer peripheral surface of the straight body portion 15b of the single crystal 15 faces the high-temperature crucible inner surface 37, The crucible inner surface 37 is heated by radiant heat. The amount of heat offsets the amount of heat released from the outer peripheral surface of the straight body 15b of the single crystal 15 to the ceiling of the container 19 and the refractory 9, so that the temperature difference in the radial direction of the single crystal 15 is reduced, and The crystal grows uniformly on the surface 15 c of the single crystal 15 in contact with the liquid 25. At the time of forming the straight body portion, since a large amount of heat is radiated from the crystal portion protruding above the crucible 1, that is, the tapered surface of the tapered portion 15a, the crucible inner portion of the outer peripheral surface of the straight body portion 15b of the single crystal 15 is Even if it faces directly, the temperature does not rise, and the outer peripheral surface of the straight body portion 15b does not have surface roughness due to thermal etching. By these actions, the defect rate can be reduced without generating cracks or cracks, and a single crystal with improved quality can be grown.
[0074]
The effect of the present embodiment was calculated by numerical simulation. As a calculation condition, the crystal material is Gd having a melting point of 1950 ° C. 2 SiO 5 The temperature change due to the presence or absence of the radiant heat shield cylinder 33 as the radiant heat shield in the crucible when forming the tapered portion as in the present embodiment shown in FIGS. 5 and 7 was calculated. The temperature of the crystal growth surface under the crystal is 1950 ° C. As a result of the calculation, when the radiation heat blocking cylinder 33 is inserted as shown in FIG. 5 when the tapered portion is formed, the tapered surface of the tapered portion 15a becomes about 1730 ° C. At this time, the reflectance of the radiation heat shielding cylinder 33 is set to 1.0. If there is no radiant heat blocking cylinder 33, the tapered surface of the tapered portion 15a is about 1780 ° C., and the tapered surface has a difference of about 50 ° C. depending on the presence or absence of the radiant heat blocking cylinder, that is, the presence of the radiant heat shield in the crucible.
[0075]
As described above, according to the single crystal manufacturing technique of the present embodiment, the temperature of the tapered surface at the time of forming the tapered portion can be reduced, the surface roughness due to thermal etching can be reduced, and defects caused by the tapered surface as a source can be reduced. The occurrence of cracks can be reduced. Therefore, the defect rate in the production of a single crystal can be reduced.
[0076]
Further, in this embodiment, it is possible to grow the crystal uniformly in the plane of the crystal when forming the straight body of the crystal, and to increase the growth rate. Further, the present invention has an effect of improving controllability of crystal growth.
[0077]
(Fourth embodiment)
Hereinafter, a fourth embodiment of a single crystal manufacturing technique to which the present invention is applied will be described with reference to FIGS. FIG. 8 is a longitudinal sectional view showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a state where a tapered portion is formed in a growing process. FIG. 9 is a longitudinal sectional view showing a state near the crucible when the straight body portion is formed according to the present embodiment. Note that, in the present embodiment, the same components and operations as those in the third embodiment are denoted by the same reference numerals, description thereof is omitted, and configurations and features different from those in the third embodiment will be described.
[0078]
This embodiment is different from the third embodiment in that, instead of the radiant heat interrupting cylinder moving means and the radiant heat interrupting cylinder, an annular straight body radiant heat interrupter made of the same metal material as the crucible is used. There is provided a straight body radiation heat shield moving means for moving the body radiation heat shield up and down along the center line of the refractory. That is, as shown in FIG. 8, the single crystal manufacturing apparatus according to the present embodiment includes a radiant heat shield plate 39 and a radiant heat shield plate which are annular straight body radiant heat shields made of the same metal material as the crucible 1 or the like. A straight body radiant heat interrupter moving means for moving 39 in the vertical direction along the center line of the refractory 9 is provided.
[0079]
The straight body radiant heat shield moving means includes a rod-shaped support member 41 for supporting the radiant heat shield plate 39, a moving mechanism (not shown) for vertically moving the support member 41, and the like. The high-frequency coil 11 is lowered as a whole compared to the third embodiment so that the upper end is lower than the upper end of the crucible 1, and is higher than the liquid level of the melt 25 of the crucible 1. The heating amount of the portion is smaller than that of the third embodiment.
[0080]
The radiant heat shield plate 39 is positioned above the upper end of the refractory 9 when the tapered portion of the single crystal 15 is formed, and is positioned around the single crystal above the crucible 1 when the straight body of the single crystal 15 is formed. Therefore, the radiant heat shield plate 39 has an outer diameter substantially equal to or smaller than the inner diameter of the crucible 1, and has an inner diameter slightly larger than the outer diameter of the straight body 15b of the single crystal 15 to be grown.
[0081]
When the high-frequency coil 11 is energized, the crucible 1 is heated. However, since the high-frequency coil 11 is lowered as compared with the third embodiment, the liquid level of the melt 25 of the crucible 1 is increased. The heating amount in the upper part is smaller. In the present embodiment, when the tapered portion of the single crystal 15 is formed, as shown in FIG. 8, the radiant heat shield plate 39 is moved to the upper part of the container 19 by the straight body radiant heat shield moving means including the support member 41. It has moved above the upper end of the refractory 9.
[0082]
That is, when the tapered portion is formed, since the radiation heat shielding plate 39 is not provided, heat is radiated upward from the tapered surface of the tapered portion 15a of the single crystal 15, and the tapered surface of the tapered portion 15a can be kept at a lower temperature. The tapered surface of the tapered portion 15a directly faces the inner surface of the crucible 1, but the amount of heating by the high-frequency coil 11 above the liquid surface of the melt 25 of the crucible 1 is reduced. The amount of heat is smaller than the amount of heat dissipated, so that the tapered surface of the tapered portion 15a is kept at a low temperature, and surface roughness due to high temperature is avoided.
[0083]
The formation of the tapered surface of the tapered portion 15a is completed, and in the process of forming the straight body portion, as shown in FIG. 9, the radiation heat shielding plate 39 is lowered from the position shown in FIG. Crystal 15 is arranged around straight body 15 b so as to close the gap between the upper end of crucible 1 and the outer peripheral surface of straight body 15 b of single crystal 15. For this reason, heat radiation from the outer peripheral surface of the straight body portion 15b of the single crystal 15 inside the crucible 1 is reduced, the temperature difference in the radial direction of the single crystal 15 is reduced, and the occurrence of defects and cracks is reduced. The defect rate in the production of a single crystal is reduced.
[0084]
Further, the crystal grows uniformly over the entire surface 15 c of single crystal 15 in contact with melt 25. In addition, since there is nothing to block heat radiation from the tapered surface of the tapered portion 15a, the cooling speed of the crystal growth surface is increased, and the crystal growth speed can be kept high. Further, since the radiant heat shield plate 39 is made of metal, the radiant heat shield plate 21 also has a high temperature due to the high frequency heating, and has an effect of heating the inside of the crucible 1.
[0085]
In FIG. 9, the radiant heat shielding plate 39 is arranged around the straight body 15b of the single crystal 15 above the crucible 1 so as to close the gap between the upper end of the crucible 1 and the outer peripheral surface of the straight body 15b of the single crystal 15. This position is desirable because it most suppresses heat radiation from the outer peripheral surface of the straight body portion 15b. However, even if the radiation heat shield plate 39 is further lowered and arranged at a position inside the crucible 1, a temperature drop on the outer peripheral surface of the straight body portion 15b at a position close to the liquid level of the melt 25 can be suppressed. Therefore, substantially the same effect as in the case of the position shown in FIG. 9 can be obtained.
[0086]
The radiation heat shielding plate 39 is an annular body having an inner diameter larger than the outer diameter of the straight body portion 15b of the single crystal 15, smaller than the inner diameter of the crucible 1, and having an outer diameter larger than the outer diameter of the crucible 1. The radiant heat shield plate is positioned close to the upper end of the crucible 1 when the single crystal straight body is formed, and is moved upward from the upper end of the crucible 1 when the tapered portion of the single crystal 15 is formed. This has the same effect.
[0087]
(Fifth embodiment)
Hereinafter, a fifth embodiment of a single crystal manufacturing technique to which the present invention is applied will be described with reference to FIGS. 10 and 11 are longitudinal sectional views near a crucible showing a schematic configuration of a single crystal manufacturing apparatus to which the present invention is applied in a state where a tapered portion is formed in a growing process. In the present embodiment, the same components and operations as those in the third and fourth embodiments are denoted by the same reference numerals, and description thereof will be omitted. Configurations and features different from those in the third and fourth embodiments will be described. Will be described.
[0088]
The present embodiment is different from the third embodiment in that instead of the radiation heat shielding cylinder 33 and the radiation heat shielding cylinder moving means shown in FIG. A radiant heat shield in a crucible made of a nonmetallic material and a radiant heat shield moving means for moving the radiant heat shield in the crucible up and down along the center line of the refractory are provided. That is, as shown in FIG. 10, the single crystal manufacturing apparatus according to the present embodiment is a radiant heat shield in a crucible made of a non-metallic material having a conical shape along the tapered portion 15a of the single crystal 15. There is provided a radiant heat shield moving means in a crucible for moving the radiant heat shield plate 43 up and down along the center line of the refractory 9 including the shield plate 43 and a rod-shaped support member 45 for supporting the radiant heat shield plate 43. The radiant heat shield moving means in the crucible includes a rod-like support member 45 that supports the radiant heat shield plate 43 and extends in the vertical direction, and a moving mechanism (not shown) for moving the support member 45 in the vertical direction. It is configured.
[0089]
In the present embodiment, when the tapered portion of the single crystal 15 is formed, as shown in FIG. 10, the radiation heat shielding plate 43 is located near the tapered surface of the tapered portion 15 a of the single crystal 15. The inclination angle of the conical surface of the radiation heat shielding plate 43 is substantially the same as the inclination angle of the tapered surface of the tapered portion 15a. Further, as shown in FIG. 11, when forming the straight body portion of single crystal 15, radiation heat shielding plate 43 has moved to a position away from the tapered surface of tapered portion 15 a of single crystal 15.
[0090]
The operation of the radiant heat shield plate 43 of this embodiment is the same as the operation of the radiant heat shield cylinder 33 of the third embodiment, and when the tapered portion of the single crystal 15 is formed, the tapered portion 15a of the single crystal 15 is formed. The radiation heat shielding plate 43 is arranged near the tapered surface, and when forming the straight body of the single crystal 15, the radiation heat shielding plate 43 is moved to a position away from the tapered surface of the tapered portion 15 a of the single crystal 15. .
[0091]
In the present embodiment, since the inclination angle of the conical surface of the radiation heat shielding plate 43 is substantially the same as the inclination angle of the tapered surface of the tapered portion 15a, the tapered portion is formed at any position on the tapered surface of the tapered portion 15a when the tapered portion is formed. Since the tapered portion 15a is formed in a state where the interval between the tapered surface of the portion 15a and the radiation heat shielding plate 43 is the same, the entire tapered surface of the tapered portion 15a can be formed uniformly, and cracks, that is, cracks are less likely to occur. In addition, the defective rate in the production of a single crystal can be reduced.
[0092]
In addition, since the radiation heat shielding plate 43 is not in a position close to the tapered surface of the tapered portion 15a at the time of forming the straight body, heat radiation from the tapered surface of the tapered portion 15a can be increased to increase the growth rate.
[0093]
That is, according to this embodiment, the same effects as those of the other embodiments can be obtained.
[0094]
It is to be noted that the surface roughness can be prevented by using not only a conical plate as shown in FIG. 10 but also a flat circular plate as the radiant heat shield plate 43, but the inclination of the tapered surface to be formed is matched. It is desirable to use a conical plate.
[0095]
(Sixth embodiment)
A sixth embodiment of a single crystal manufacturing apparatus to which the present invention is applied will be described with reference to FIGS. FIG. 12 is a longitudinal sectional view showing a schematic configuration and operation of a single crystal manufacturing apparatus to which the present invention is applied, and is a diagram showing a stage of growing a taper portion of a single crystal. FIG. 13 is a longitudinal sectional view showing a schematic configuration and operation of a single crystal manufacturing apparatus to which the present invention is applied, and is a diagram showing a stage of growing a straight body of a single crystal. FIG. 14 is a diagram comparing the distribution of the calorific value in the height direction of the side wall of the single crystal manufacturing apparatus to which the present invention is applied and the conventional single crystal manufacturing apparatus. FIG. 15 is a diagram comparing the temperature distribution in the height direction of the side wall between the single crystal manufacturing apparatus to which the present invention is applied and the conventional single crystal manufacturing apparatus. In the present embodiment, the same components and operations as those in the first to fifth embodiments are denoted by the same reference numerals.
[0096]
As shown in FIG. 12, the apparatus for manufacturing a single crystal according to the present embodiment includes a cylindrical crucible 1, a ring-shaped member 47 attached to an outer surface of a side wall of the crucible 1 and serving as a wall-side heating member, and a refractory surrounding the crucible 1. 9, a high frequency generating means 49 for generating a high frequency outside the refractory 9, and a crystal moving means 51 for holding a seed crystal and rotating the crystal to pull it upward.
[0097]
The apparatus for manufacturing a single crystal according to the present embodiment is an apparatus for manufacturing a single crystal having a melting point of 1500 ° C. or higher. The crucible 1 has a cylindrical shape in which an upper end portion 1c is opened, a lower end portion 1d is closed, and a bottom 1b is formed. The container is made of a conductive, high-melting metal material, such as iridium, platinum, tungsten, or molybdenum. The ring-shaped member 47 is provided on the outer surface of the side wall 1a of the crucible 1 in a ring shape along the circumferential direction of the outer surface of the side wall 1a, and is a projecting member that projects laterally from the outer surface of the side wall 1a. is there.
[0098]
Such a ring-shaped member 47 is made of a metal material having high conductivity and high melting point, for example, iridium, platinum, tungsten, molybdenum or the like, like the crucible 1, and can also be formed integrally with the crucible 1. And what was formed separately from the crucible 1 can be attached to the side wall of the crucible 1. When the ring-shaped member 47 is formed separately from the crucible 1, the ring-shaped member 47 can be formed of the same material as the material forming the crucible 1, or can be formed of a different material. When the ring-shaped member 47 is formed separately from the crucible 1, it is desirable that the ring-shaped member 47 is attached in a state in which the ring-shaped member 47 comes into contact with the crucible 1 as strongly as possible. In this embodiment, two ring-shaped members 47 are provided at intervals between the upper end portion 1c and the lower end portion 1d of the outer surface of the side wall 1a of the crucible 1.
[0099]
The refractory 9 is a cylindrical container larger in size than the crucible 1 in which the upper end is opened and the lower end is closed and the bottom is formed. The refractory 9 is a high temperature resistant material having insulation and heat insulation, such as zirconia or alumina. The crucible 1 in which a ring-shaped member 47 is provided is accommodated. The high-frequency generating means 49 is provided outside the refractory 9 at a position corresponding to the side wall 1 a of the crucible 1, surrounding the high-frequency coil 11 installed around the refractory 9, and via the high-frequency coil 11 and the wiring 53. It is composed of an electrically connected high frequency power supply 55 and the like. The crystal moving means 51 includes a rod-shaped or band-shaped seed holder 17, a driving unit 57 that suspends the seed holder 17 and pulls up while rotating the seed holder 17. The driving unit 57 supports the seed holder 17 in a state where the seed holder 17 is suspended from above the opening at the upper end of the refractory 9 toward the center of the opening of the crucible 1. The seed crystal 13 is attached to the tip of the.
[0100]
The operation of the apparatus for manufacturing a single crystal having such a configuration and the features of the present invention will be described. When a high-frequency current flows from the high-frequency power supply 55 to the high-frequency coil 11 in a state in which the raw material is stored in the crucible 1, an induced current flows through the conductive crucible 1. As a result, the crucible 1 is heated by Joule heating, and the raw material in the crucible 1 that has been heated is melted to be in a molten state, and the melt 25 is formed. When the seed crystal 13 attached to the tip of the seed holder 17 is pulled up from the melt 25, a single crystal 15 is generated. When the single crystal 15 is generated, first, a tapered portion 15a is formed in a conical shape continuous with the seed crystal 13, and continuous with the tapered portion 15a, as shown in FIG. Is formed. When the single crystal 15 is pulled up from the melt 25, a flow from the single crystal 15 toward the inner surface of the side wall 1 a of the crucible 1 near the liquid surface of the melt 25, that is, a flow expanding in the radial direction from the position of the single crystal 15 The single crystal 15 is rotated by rotating the seed holder 17 about a rotation axis.
[0101]
Here, since the electromagnetic field generated by the high-frequency coil 11 is concentrated particularly at the corners, it generates more heat at the upper end portion 1c and the lower end portion 1d of the crucible 1 than at other portions. Further, in the present embodiment, the ring-shaped member 47 installed between the upper end portion 1c and the lower end portion 1d of the outer surface of the side wall 1a of the crucible 1 also has the same shape as the upper end portion 1c and the lower end portion 1d of the crucible 1. It generates more heat than other parts.
[0102]
Therefore, as shown by a heat generation amount distribution 101 shown by a solid line in FIG. 14, the heat generation amount of the side wall 1a per unit volume increases in order from the bottom 1b of the crucible 1 toward the upper end portion 1c, that is, in the height direction. The peripheral portion of the bottom 1b of 1a, that is, the lower end portion 1d, the portion provided with the lower ring-shaped member 47, the portion provided with the upper ring-shaped member 47, and the peak at the upper end portion 1c of the side wall 1a. Distributed so that As a result, the temperature distribution of the side wall 1a of the crucible 1 also increases in the direction from the bottom 1b of the crucible 1 toward the upper end portion 1c, that is, in the height direction, as shown by the temperature distribution 105 shown by the solid line in FIG. It peaks at the bottom 1b, the lower part provided with the ring-shaped member 47, the upper part provided with the ring-shaped member 47, and the upper end part 1c of the side wall 1a.
[0103]
By the way, in the conventional single crystal manufacturing apparatus in which the ring-shaped member 47 is not provided, the calorific value of the side wall per unit volume is, as shown by a calorific value distribution 103 shown by a broken line in FIG. In order from the top to the upper end portion, that is, the height direction, the peaks are distributed only at the peripheral portion at the bottom of the side wall, that is, at the lower end portion, and only at the upper end portion of the side wall. As a result, the temperature distribution on the side wall of the crucible also increases in the order from the bottom of the crucible toward the upper end portion, that is, in the height direction, as shown by the temperature distribution 107 shown by the broken line in FIG. The peak occurs only at the upper end portion of the side wall. That is, in the conventional single crystal manufacturing apparatus, the calorific value and the temperature of the lower end portion and the upper end portion of the side wall are higher than those of the other portions, and the distribution of the calorific value and the temperature are non-uniform. As the distance between the lower end portion and the upper end portion of the side wall increases, the calorific value and the temperature at the portion between the lower end portion and the upper end portion of the side wall decrease, so that such a distribution of the calorific value and the temperature is not sufficient. The uniform state is particularly large when using a crucible whose height is higher than the diameter of the bottom or a large crucible whose diameter and height of the bottom are several tens of cm or more.
[0104]
Therefore, in the conventional single crystal manufacturing apparatus, the distribution of the calorific value and the temperature in the height direction of the side wall 1a is not uniform due to the conditions such as the size and shape of the crucible, and the lower end portion 1d and the upper end portion 1c of the side wall 1a are not uniform. When the temperature of the portion in between is low, as shown in FIG. 16, the melt 25 in the crucible 1 is heated by the lower end portion 1d of the crucible 1, expands, and first rises along the inner surface of the side wall 1a of the crucible 1. However, at a middle height of the side wall 1 a of the crucible 1, the temperature becomes low, so that it flows away from the side wall 1 a, interferes with the flow of the melt 25 in the upper part of the crucible 1, and exhibits a complicated convection pattern, The flow of the entire melt 25 in the crucible 1 is disturbed.
[0105]
As a result, the shape of the single crystal growing portion of the single crystal 15 formed continuously with the seed crystal 13, that is, the solid-liquid interface portion 59 is disturbed, resulting in an uneven state. If the shape of the solid-liquid interface portion 59 of the single crystal 15 is disturbed and becomes uneven, the temperature distribution in the solid-liquid interface portion 59 of the single crystal 15 and the vicinity thereof becomes non-uniform, and distortion occurs in the single crystal 15. For example, the quality of the single crystal 15 deteriorates. In addition, when strain occurs in the single crystal 15, a problem such as breaking of the crystal occurs when the grown single crystal 15 is cooled.
[0106]
On the other hand, in the single crystal manufacturing apparatus of the present embodiment, as described above, since the ring-shaped member 47 is provided on the crucible 1, the calorific value of the side wall 1a is reduced by the lower end portion 1d of the side wall 1a and the upper end. In addition to the portion 1c, the portion where the lower ring-shaped member 47 is provided and the portion where the upper ring-shaped member 47 is provided are higher than other portions. The lower portion 1d of the side wall 1a and the lower ring-shaped member 47 are formed by increasing the amount of heat generated in the portion provided with the lower ring-shaped member 47 and the portion provided with the upper ring-shaped member 47. The calorific value of the provided portion, the portion provided with the upper ring-shaped member 47, and the portion other than the upper end portion 1c is also higher than that of the conventional single crystal manufacturing apparatus. In comparison, the calorific value distribution in the height direction of the side wall is made uniform.
[0107]
Thus, in the single crystal manufacturing apparatus according to the present embodiment, the temperature at the side wall 1a depends on the lower ring portion 47 and the upper ring portion in addition to the lower end portion 1d and the upper end portion 1c of the side wall 1a. It is higher than the other portions at the portion where the shaped member 47 is provided. The lower portion 1d of the side wall 1a and the lower ring-shaped member 47 are provided by increasing the temperature of the portion where the lower ring-shaped member 47 is provided and the temperature of the portion where the upper ring-shaped member 47 is provided. The calorific value of the portion provided, the portion provided with the upper ring-shaped member 47, and the portion other than the upper end portion 1c is also higher than that of the conventional single crystal manufacturing apparatus, and is higher than that of the conventional single crystal manufacturing apparatus. The temperature distribution in the height direction of the side wall is made uniform. When the distribution of the calorific value and the temperature in the height direction of the side wall 1a of the crucible 1 are made uniform in this way, as shown in FIGS. 12 and 13, the melt 25 in the crucible 1 is applied to the side wall of the crucible 1 by natural convection. Since a flow that rises smoothly along the inner surface of 1a is formed, it is difficult to exhibit an undesirably complicated convection pattern as in a conventional single crystal manufacturing apparatus.
[0108]
As described above, in the single crystal manufacturing apparatus of the present embodiment, since the ring-shaped member 47 is provided at the portion between the lower end portion 1d and the upper end portion 1c of the side wall 1a, as described above, By driving 49, in addition to the lower end portion 1d and the upper end portion 1c of the side wall 1a, the lower ring member 47 and the upper ring member 47 also generate heat, and the temperature distribution in the height direction of the side wall 1a of the crucible 1 is reduced. Make uniform. For this reason, the heat generation distribution in the height direction of the side wall 1a of the crucible 1 can be controlled, and the convection of the melt 25 in the crucible 1 can be controlled. Since a flow that rises smoothly along the inner surface of the crucible 1a can be formed, the melt 25 in the crucible 1 hardly exhibits an undesirable convection pattern as in the related art. Therefore, the solid-liquid interface portion of the single crystal can be flattened irrespective of conditions such as the size and shape of the crucible, and the occurrence of defects and cracks can be reduced, and the defect rate in the production of the single crystal can be reduced.
[0109]
Further, since the solid-liquid interface portion of the single crystal can be flattened, the quality of the obtained single crystal can be improved. In addition, the quality of the single crystal can be improved, and the occurrence of cracks in the crystal can be suppressed, so that the productivity of the single crystal can be improved.
[0110]
Further, in the present embodiment, the ring-shaped members 47 are provided in two upper and lower stages, but the ring-shaped members 47 may be provided in one stage, or may be provided in three or more stages. The number of steps on which the ring-shaped member 47 is provided is appropriately determined according to the size of the crucible and the like.
[0111]
Further, in the present embodiment, the ring-shaped member 47 provided in the circumferential direction on the outer surface of the side wall 1a of the crucible 1 is used as the wall-side heating member. If it extends in the circumferential direction, it is not necessary to have a series of ring-shaped forms, and various forms can be adopted. For example, the wall-side heating member may be configured by a member piece or the like that intermittently continues in a ring shape at appropriate intervals in the circumferential direction of the outer surface of the side wall 1a of the crucible 1. In this case, the member piece needs to have a shape extending longer in the circumferential direction of the outer surface of the side wall 1a than in the height direction of the side wall 1a of the crucible 1. Further, in order to uniformly heat the side wall of the crucible 1, It is desirable to provide such member pieces at equal intervals.
[0112]
(Seventh embodiment)
Hereinafter, a seventh embodiment of a single crystal manufacturing apparatus to which the present invention is applied will be described with reference to FIGS. FIG. 17 is a cross-sectional view illustrating a schematic configuration and operation of a single crystal manufacturing apparatus to which the present invention is applied, and is a diagram illustrating a stage of growing a taper portion of a single crystal. FIG. 18 is a diagram comparing the temperature distribution at the bottom of a single crystal manufacturing apparatus to which the present invention is applied and a conventional single crystal manufacturing apparatus. In the present embodiment, the same components and operations as those in the sixth embodiment are denoted by the same reference numerals, description thereof will be omitted, and configurations and features different from those in the sixth embodiment will be described.
[0113]
The difference between the single crystal manufacturing apparatus of the present embodiment and the sixth embodiment is that, in addition to the ring-shaped member as the wall-side heating member, a bottom-side heating member for heating the central portion of the bottom of the crucible is provided. It has been provided. That is, as shown in FIG. 17, the apparatus for manufacturing a single crystal according to the present embodiment includes a heat transfer portion 61 formed of a columnar or disk-shaped member provided at the center of the outer surface of the bottom 1b of the crucible 1, and The portion 61 includes a bottom-side heating member 65 composed of a disc-shaped heat generating portion 63 provided at a central portion. The heat generating portion 63 has a diameter larger than the diameter of the heat transfer portion 61 and is formed to have a diameter that is ／ or more of the diameter of the bottom 1 b of the crucible 1. By setting the diameter of the heat generating portion 63 to 2/3 or more of the diameter of the bottom 1b of the crucible 1, the heat generating portion 63 can easily generate heat by the high-frequency electromagnetic field, and the heating capability of the bottom heating member 65 can be improved. The bottom heating member 65 provided on the bottom 1 b side of the crucible 1 is housed in the refractory 9 together with the crucible 1.
[0114]
The bottom heating member 65 composed of the heat transfer portion 61 and the heat generation portion 63 is made of a conductive and high-melting metal material such as iridium, platinum, tungsten, molybdenum, etc., like the crucible 1 and the ring-shaped member 47. The crucible 1 is formed so as to be continuous with the bottom 1b of the crucible 1 and can be formed integrally with the crucible 1, or can be formed separately from the crucible 1 and attached to the bottom 1b of the crucible 1. Further, the heat transfer section 61 and the heat generation section 63 of the bottom side heating member 65 can be formed separately. When the bottom side heating member 65 is formed separately from the crucible 1, the bottom side heating member 65 can be formed of the same material as the material forming the crucible 1, or can be formed of a different material. When the bottom-side heating member 65 is formed separately from the crucible 1, it is desirable that the bottom-side heating member 65 is attached in a state where the heat transfer section 61 is in contact with the crucible 1 as strongly as possible.
[0115]
In the single crystal manufacturing apparatus of the present embodiment having such a configuration, the electromagnetic field generated by the high-frequency coil 11 is concentrated particularly at the corners, and therefore, the peripheral portion of the bottom 1b of the crucible 1, that is, the lower end 1d of the crucible 1 In addition to the above, heat is generated also at the peripheral portion of the heat generating portion 63 of the bottom side heating member 65. The heat generated at the peripheral portion of the heat generating portion 63 of the bottom-side heating member 65 is transmitted from the heat generating portion 63 to the central portion of the bottom 1b of the crucible 1 through the heat transfer portion 61 by heat conduction. Is heated at the center. Therefore, the calorific value of the bottom 1b per unit volume is distributed so as to peak at the center of the bottom 1b in addition to the peripheral portion of the bottom 1b of the crucible 1. As a result, the temperature distribution at the bottom 1b of the crucible 1 also peaks at the central portion of the bottom 1b in addition to the peripheral portion of the bottom 1b of the crucible 1, as shown by the temperature distribution 201 shown by the solid line in FIG.
[0116]
On the other hand, in the conventional single crystal manufacturing apparatus in which the bottom side heating member 65 is not provided, the calorific value of the bottom per unit volume is distributed such that it becomes a peak only at the peripheral portion of the bottom of the crucible 1. I do. As a result, the temperature distribution on the side wall of the crucible also reaches a peak only at the peripheral portion at the bottom of the crucible as shown by the temperature distribution 203 indicated by the broken line in FIG. That is, in the conventional single crystal manufacturing apparatus, the temperature at the center of the bottom of the crucible is the lowest. The temperature at the center of the crucible bottom decreases as the diameter of the crucible bottom increases. Therefore, in the conventional single crystal manufacturing apparatus, the flow of the melt rising from the central portion of the bottom of the crucible is not formed due to conditions such as the size and shape of the crucible, and the side wall of the crucible from the solid-liquid interface portion of the single crystal. There is a case where the flow of the melt expanding in the radial direction toward the inner surface is not formed. For this reason, the shape of the solid-liquid interface portion of the single crystal formed continuously with the seed crystal is disturbed and becomes uneven, so that a poor quality crystal is generated or the crystal is cracked.
[0117]
Conventionally, even if the temperature of the central part of the bottom of the crucible is low and the flow of the melt expanding in the radial direction from the solid-liquid interface part of the single crystal toward the inner surface of the side wall of the crucible is not formed, the crystal is pulled when the single crystal is pulled up. By rotating the melt, it is possible to form a flow of the melt expanding in the radial direction from the single crystal toward the inner surface of the side wall of the crucible. However, in the stage of forming the tapered portion of the single crystal from the seed crystal, even if the crystal is rotated, the centrifugal force generated by the rotation of the crystal is small because the diameter of the tapered portion of the seed crystal or single crystal is small, and The flow expanding in the radial direction is weaker than the stage after the single-crystal straight body portion starts to be formed. Therefore, it is difficult to flatten the solid-liquid interface of the single crystal only by rotating the crystal. Such a situation similarly occurs even when only the wall-side heating member is provided in the crucible as in the single crystal manufacturing apparatus of the first embodiment.
[0118]
On the other hand, in the single crystal manufacturing apparatus of the present embodiment, as shown in FIG. 17, since the bottom heating member 65 is provided in the crucible 1, the calorific value at the bottom 1 b of the crucible 1 is In addition to the peripheral portion, the center portion is also higher than the other portions. Then, as the calorific value of the central portion of the bottom 1b increases, the temperature of the bottom 1b of the crucible 1 becomes higher than the other portions in addition to the peripheral portion of the bottom 1b. When the temperature of the central portion of the bottom 1b increases, the vicinity of the central axis of the crucible 1 rises along the central axis from the central portion of the bottom 1b, and the vicinity of the solid-liquid interface portion 59 of the seed crystal 13 or the single crystal 15 And a flow of the melt 31 is formed which expands in the radial direction from the vicinity of the solid-liquid interface portion 59 of the seed crystal 13 or the single crystal 15 toward the inner surface of the side wall 1 a of the crucible 1.
[0119]
As described above, in the single crystal manufacturing apparatus of the present embodiment, since the bottom-side heating member 65 that heats the central portion of the bottom 1b of the crucible 1 is provided, as described above, In addition to the peripheral portion of the bottom 1b of the crucible 1, the central portion is also heated. For this reason, it rises from the central portion of the bottom 1 b of the crucible 1 and reaches near the solid-liquid interface portion 59 of the seed crystal 13 and the single crystal 15, and from the vicinity of the solid-liquid interface portion 59 of the seed crystal 13 and the single crystal 15. The flow of the melt 25 spreading in the radial direction toward the inner surface of the side wall 1a is formed. Therefore, regardless of conditions such as the size and shape of the crucible, the solid-liquid interface portion of the single crystal can be flattened, the occurrence of defects and cracks can be reduced, and the defect rate in the production of the single crystal can be reduced. .
[0120]
Further, in the present embodiment, the ring-shaped member 47 as the wall-side heating member is provided. However, when the wall-side heating member is not required due to the size and shape of the crucible, the ring-shaped member as the wall-side heating member is used. It is also possible to adopt a configuration in which the member 47 is not provided.
[0121]
Further, in the present embodiment, the bottom-side heating member 65 including the heat-transfer portion 61 formed of a columnar or disk-shaped member and the disk-shaped heat generation portion 63 is provided. Heat can be generated by the generation means 49, and various configurations can be adopted in which the central portion of the bottom 1b of the crucible 1 can be heated.
[0122]
For example, as shown in FIG. 19, a member on a disk made of a conductive and high-melting metal material is installed on the bottom surface in the refractory 9 to form a heat generating portion 67. A heat insulating member 71 having a through hole 69 formed in the center and having the same diameter as the inner diameter of the refractory 9 is installed. Then, the crucible 1 is placed on the heat insulating member 71 by aligning the central portion of the bottom 1 b of the crucible 1 with the position of the through hole 69 of the heat insulating member 71. In such a bottom-side heating member 73, the heat generated at the peripheral portion of the heat-generating portion 67 is collected at the central portion of the heat-generating portion 67 by heat conduction, and radiated through the through-hole 69 to form the center of the bottom 1 b of the crucible 1. Heat the parts. As described above, the bottom-side heating member may be constituted by the heat-insulating member 71 forming the heat transfer portion, such as the bottom-side heating member 73, and the heat generating portion 67, which is a member on the disk. If the bottom heating member is configured like the bottom heating member 73, the number of parts can be reduced.
[0123]
In addition, the bottom side heating member, the heat generating portion was formed in a circular ring shape with a conductive and high melting point metal material, and formed of a conductive and high melting point metal material coaxially with the heat generating portion. A configuration in which a cylindrical heat transfer portion is arranged, and a rod-shaped connecting member formed of a high melting point metal material is provided in a spoke shape between the heat generation portion and the heat transfer portion can be adopted. Note that, in the bottom-side heating member having various configurations, the heat transfer portion does not need to be in the shape of a disk or a column, but may be in the shape of a prism.
[0124]
In the sixth and seventh embodiments, the ring-shaped member 47 and the bottom-side heating member 65, which are wall-side heating members, are fixed to the crucible 1. However, the wall-side heating member and the bottom-side heating member 65 are fixed. The heating member may be configured to be detachable so that the heating member can be detached from the crucible when unnecessary. Further, a mechanism for attaching and detaching the wall-side heating member and the bottom-side heating member to and from the crucible 1 may be provided. For example, as shown in FIG. 20, a heat insulating member 77 having a through hole 75 formed in a central portion above the bottom 9 c in the refractory 9 and having the same diameter as the inner diameter of the refractory 9 is installed. Between the bottom 9c in the refractory 9 and the heat insulating member 77, a bottom heating member 65 having the same configuration as that of the seventh embodiment and formed separately from the crucible 1 is installed. However, a connecting member 79 provided through the bottom of the refractory 9 is connected to the lower surface of the heat generating portion 63 of the bottom heating member 65. The connecting member 79 is connected to a driving unit 81 for moving the bottom heating member 65 up and down, for example, a hydraulic or air jack, a motor and a rack and pinion type driving mechanism, and the connecting member 79 and the driving unit 81 are connected to each other. The heating member moving means 83 is included.
[0125]
With such a configuration including the heating member moving means 83, the heat transfer portion 61 of the bottom heating member 65 is detached from the bottom 1b of the crucible 1 as necessary, and the heating of the central portion of the bottom 1b is stopped. be able to. That is, at the stage of forming the tapered portion 15 a of the single crystal 15 from the seed crystal 13, the heating member moving means 83 pushes up the bottom heating member 65, and the heat transfer portion 61 of the bottom heating member 65 is moved to the crucible 1. When the diameter of the tapered portion 15a of the single crystal 15 becomes sufficiently large, the bottom heating member 65 is lowered by the heating member moving means 83, and the heat of the bottom heating member 65 is reduced to the bottom of the crucible 1. Heat is not transferred to the central part of 1b. In addition, the structure provided with such a heating member moving means can be applied to the wall side heating member. With this configuration, the solid-liquid interface portion 59 of the single crystal 15 can be controlled to an optimum state, and a higher quality single crystal can be obtained.
[0126]
The single crystal manufacturing techniques described in the first to seventh embodiments can be used in appropriate combinations.
[0127]
Further, the present invention is not limited to the manufacturing apparatuses having the configurations of the first to seventh embodiments, but can be applied to single crystal manufacturing apparatuses having various configurations for heating a crucible by high frequency. Further, the apparatus for producing a single crystal to which the present invention is applied is particularly effective for growing oxide single crystals such as gadolinium, gallium, garnet, and cerium-activated gadolinium silicate. Can be used for the production of
[0128]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the defect rate in manufacture of a single crystal can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a first embodiment of a single crystal manufacturing apparatus to which the present invention is applied in a cooling process.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a first embodiment of a single crystal manufacturing apparatus to which the present invention is applied in a growing process.
FIG. 3 is a longitudinal sectional view showing a modification of the single crystal manufacturing apparatus of the first embodiment.
FIG. 4 is a longitudinal sectional view showing a schematic configuration of a second embodiment of a single crystal manufacturing apparatus to which the present invention is applied in a growing process.
FIG. 5 is a longitudinal sectional view showing a schematic configuration of a third embodiment of a single crystal manufacturing apparatus to which the present invention is applied, in a state where a tapered portion is formed in a growing process.
FIG. 6 is a perspective view of the vicinity of the crucible shown so that the arrangement of the radiant heat shield cylinder when forming the tapered portion of the single crystal can be understood.
FIG. 7 is a longitudinal sectional view showing a state when a straight body is formed in a process of growing the single crystal manufacturing apparatus shown in FIG. 5;
FIG. 8 is a longitudinal sectional view showing a schematic configuration of a fourth embodiment of a single crystal manufacturing apparatus to which the present invention is applied, in a state where a tapered portion is formed in a growing process.
FIG. 9 is a longitudinal sectional view showing a state near a crucible when a straight body is formed in a fourth embodiment.
FIG. 10 is a longitudinal sectional view near a crucible showing a schematic configuration of a fifth embodiment of a single crystal manufacturing apparatus to which the present invention is applied, in a state where a tapered portion is formed in a growing process.
FIG. 11 is a longitudinal sectional view near a crucible showing a schematic configuration of a fifth embodiment of a single crystal manufacturing apparatus to which the present invention is applied, when a tapered portion is formed in a growing process.
FIG. 12 is a longitudinal sectional view showing a schematic configuration and operation of a sixth embodiment of a single crystal manufacturing apparatus to which the present invention is applied, and is a view showing a stage of growing a taper portion of a single crystal.
FIG. 13 is a cross-sectional view showing a schematic configuration and operation of a single crystal manufacturing apparatus according to a sixth embodiment of the present invention, showing a stage of growing a single crystal straight body.
FIG. 14 is a diagram comparing the distribution of heat generation in the height direction of the side wall of the single crystal manufacturing apparatus of the sixth embodiment and a conventional single crystal manufacturing apparatus.
FIG. 15 is a diagram comparing the temperature distribution in the height direction of the side wall between the single crystal manufacturing apparatus of the sixth embodiment and the conventional single crystal manufacturing apparatus.
FIG. 16 is a view showing a state of convection of a melt in a crucible in a conventional single crystal manufacturing apparatus.
FIG. 17 is a cross-sectional view showing a schematic configuration and operation of a seventh embodiment of a single crystal manufacturing apparatus to which the present invention is applied, and is a diagram showing a stage of growing a taper portion of a single crystal.
FIG. 18 is a diagram comparing the temperature distribution at the bottom of the single crystal manufacturing apparatus of the seventh embodiment with the conventional single crystal manufacturing apparatus.
FIG. 19 is a cross-sectional view showing a modification of the seventh embodiment of the single crystal manufacturing apparatus to which the present invention is applied.
FIG. 20 is a sectional view showing another modified example of the seventh embodiment of the single crystal manufacturing apparatus to which the present invention is applied.
[Explanation of symbols]
1 Crucible
3 Heat transfer member
7 Radiation heat blocking member
11 High frequency coil
13 seed crystal
15 Single crystal
15a taper part
15b straight body
17 Seed holder

Claims (12)

原料を収容するルツボと、該ルツボ内の原料を加熱する加熱手段と、種結晶を前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
少なくとも前記ルツボの側壁の上端部分近傍から上方に延在し、形成される単結晶を囲み、伝熱性を有する材料で形成した伝熱部材を設けたことを特徴とする単結晶の製造装置。A crucible containing a raw material, a heating means for heating the raw material in the crucible, and a single crystal manufacturing apparatus including a crystal moving means for moving a seed crystal upward from the inside of the crucible,
An apparatus for manufacturing a single crystal, comprising a heat transfer member extending upward from at least the vicinity of an upper end portion of a side wall of the crucible, surrounding the formed single crystal, and formed of a material having heat conductivity. 原料を収容するルツボと、該ルツボ内の原料を加熱する加熱手段と、種結晶を前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
少なくとも単結晶育成後の冷却時に、形成された単結晶の種結晶に連続して漸次拡径するテーパ部と形成された単結晶のテーパ部に連続する円柱状の直胴部との境界部分から上方への放射熱を遮断する境界部分放射熱遮断体を設けたことを特徴とする単結晶の製造装置。A crucible containing a raw material, a heating means for heating the raw material in the crucible, and a single crystal manufacturing apparatus including a crystal moving means for moving a seed crystal upward from the inside of the crucible,
At least at the time of cooling after the growth of the single crystal, from the boundary between the tapered portion that gradually and continuously expands in the formed single crystal seed crystal and the columnar straight body that is continuous with the formed single crystal tapered portion An apparatus for producing a single crystal, comprising a radiant heat shield at a boundary portion for blocking upward radiant heat. 原料を入れたルツボを加熱し、原料の融液に種結晶を接触させながら引き上げて単結晶を製造する単結晶の製造方法であって、
単結晶の直径を大きくする単結晶の成長初期の単結晶のテーパ部形成時及びテーパ部に連続して円柱状に成長する単結晶の直胴部形成時のうち、単結晶のテーパ部形成時には、前記ルツボの内面から単結晶のテーパ部に到達するの放射熱を遮断することを特徴とする単結晶の製造方法。A method for producing a single crystal, comprising heating a crucible containing a raw material and pulling up a single crystal by bringing a seed crystal into contact with a melt of the raw material,
At the time of forming the tapered portion of the single crystal in the initial stage of the growth of the single crystal to increase the diameter of the single crystal, and at the time of forming the tapered portion of the single crystal, the straight body portion of the single crystal that grows in a cylindrical shape continuously to the tapered portion is formed. A method for manufacturing a single crystal, wherein radiant heat reaching a tapered portion of the single crystal from the inner surface of the crucible is blocked. 原料を収容するルツボと、該ルツボ内の原料を加熱する加熱手段と、種結晶を前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
単結晶を囲み、前記ルツボの内面から該ルツボ内に位置する単結晶に向かう放射熱を遮断するルツボ内放射熱遮断体と、該ルツボ内放射熱遮断体を上下方向に移動させるルツボ内放射熱遮断体移動手段とを設け、該ルツボ内放射熱遮断体移動手段は、単結晶成長初期の単結晶の直径を大きくする単結晶のテーパ部形成時に、単結晶のテーパ部を囲む位置に前記ルツボ内放射熱遮断体を移動させ、テーパ部に連続して円柱状に成長する単結晶の直胴部形成時には、単結晶から離れた位置に前記ルツボ内放射熱遮断体を移動させてなることを特徴とする単結晶の製造装置。A crucible containing a raw material, a heating means for heating the raw material in the crucible, and a single crystal manufacturing apparatus including a crystal moving means for moving a seed crystal upward from the inside of the crucible,
A radiant heat shield in the crucible that surrounds the single crystal and blocks radiant heat from the inner surface of the crucible toward the single crystal located in the crucible, and a radiant heat in the crucible that moves the radiant heat shield in the crucible up and down A shield moving means, wherein the radiant heat interrupter moving means in the crucible is located at a position surrounding the tapered portion of the single crystal at the time of forming the tapered portion of the single crystal to increase the diameter of the single crystal at the initial stage of single crystal growth. Moving the inner radiant heat shield and moving the radiant heat shield in the crucible to a position distant from the single crystal during the formation of the straight body portion of the single crystal that grows in a cylindrical shape continuously to the tapered portion. Characteristic single crystal manufacturing equipment. 単結晶の原料を入れたルツボの上端部分よりも下側の部分を加熱し、原料の融液に種結晶を接触させながら引き上げて単結晶を製造する単結晶の製造方法であって、
単結晶の直径を大きくする単結晶の成長初期の単結晶のテーパ部形成時及びテーパ部に連続して円柱状に成長する単結晶の直胴部形成時のうち、単結晶の直胴部形成時には、前記ルツボの上端部分から上方への放射熱を遮断することを特徴とする単結晶の製造方法。A method for producing a single crystal, comprising heating a portion below the upper end portion of a crucible containing a single crystal raw material and pulling up the single crystal by bringing the seed crystal into contact with the melt of the raw material,
When forming the tapered portion of the single crystal in the initial stage of the growth of the single crystal in which the diameter of the single crystal is increased, and when forming the straight body of the single crystal that grows in a column shape continuously to the tapered portion, the straight body of the single crystal is formed. A method for producing a single crystal, wherein the radiant heat upward from an upper end portion of the crucible is sometimes blocked. 原料を収容するルツボと、該ルツボ内の原料を加熱する加熱手段と、種結晶を前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
単結晶が挿通可能で前記ルツボの上端部分から上方への放射熱を遮断する直胴部放射熱遮断体と、該直胴部放射熱遮断体を上下方向に移動させる直胴部放射熱遮断体移動手段とを設け、前記加熱手段は、前記ルツボの上端部分よりも下側の部分を加熱し、前記直胴部放射熱遮断体移動手段は、単結晶成長初期の、単結晶の直径を大きくする単結晶のテーパ部形成時には、前記直胴部放射熱遮断体を前記ルツボの上端部分から離れた位置に移動させ、テーパ部に連続して円柱状に成長する単結晶の直胴部形成時には、前記直胴部放射熱遮断体を、単結晶の直胴部外周面と前記ルツボの内周面との間、もしくは単結晶の直胴部外周面と前記ルツボの上端部分との間に位置させてなることを特徴とする単結晶の製造装置。A crucible containing a raw material, a heating means for heating the raw material in the crucible, and a single crystal manufacturing apparatus including a crystal moving means for moving a seed crystal upward from the inside of the crucible,
A straight body radiant heat shield that allows a single crystal to pass therethrough and blocks radiant heat upward from the upper end of the crucible, and a straight body radiant heat shield that moves the straight body radiant heat shield in the vertical direction Moving means, the heating means heats a portion below the upper end of the crucible, the straight body radiant heat interrupter moving means increases the diameter of the single crystal in the initial stage of single crystal growth. At the time of forming the tapered portion of the single crystal, the straight body radiation heat shield is moved to a position away from the upper end portion of the crucible, and at the time of forming the straight body of the single crystal that grows in a cylindrical shape continuously to the tapered portion. Positioning the straight body radiation heat shield between the single crystal straight body outer peripheral surface and the inner peripheral surface of the crucible, or between the single crystal straight body outer peripheral surface and the upper end portion of the crucible An apparatus for producing a single crystal, comprising: 原料を収容するルツボと、該ルツボを囲んで設けられた高周波コイルを含む高周波発生手段と、種結晶を回転させながら前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
前記ルツボの側壁の上端部分と下端部分との間の部分を、前記高周波発生手段の作動により加熱する壁側加熱部材を設けたことを特徴とする単結晶の製造装置。An apparatus for producing a single crystal, comprising: a crucible for accommodating a raw material, high-frequency generating means including a high-frequency coil provided around the crucible, and crystal moving means for moving the seed crystal upward from inside the crucible while rotating the seed crystal And
An apparatus for producing a single crystal, comprising a wall-side heating member for heating a portion between an upper end portion and a lower end portion of a side wall of the crucible by operating the high frequency generating means. 原料を収容するルツボと、該ルツボを囲んで設けられた高周波コイルを含む高周波発生手段と、種結晶を回転させながら前記ルツボ内から上方へ移動する結晶移動手段とを備えた単結晶の製造装置であり、
前記ルツボの底に、該底の中央部分を、前記高周波発生手段の作動により加熱する底側加熱部材を設けたことを特徴とする単結晶の製造装置。An apparatus for producing a single crystal, comprising: a crucible for accommodating a raw material, high-frequency generating means including a high-frequency coil provided around the crucible, and crystal moving means for moving the seed crystal upward from inside the crucible while rotating the seed crystal And
An apparatus for producing a single crystal, wherein a bottom-side heating member for heating a central portion of the bottom of the crucible by operating the high-frequency generating means is provided at the bottom of the crucible. 前記壁側加熱部部材は、前記ルツボの側壁外面の上端部分と下端部分との間の部分に、導電性を有する材料で前記ルツボの側壁外面の周方向に沿って延在させて設けた突起状の部材で形成されていることを特徴とする請求項７に記載の単結晶の製造装置。The wall-side heating section member is provided at a portion between an upper end portion and a lower end portion of the outer surface of the side wall of the crucible, by using a conductive material and extending along the circumferential direction of the outer surface of the side wall of the crucible. The apparatus for producing a single crystal according to claim 7, wherein the apparatus is formed of a member having a shape of a circle. 前記底側加熱部材は、前記ルツボの底外面の中央部分に熱を伝える熱伝導性を有する材料で形成した伝熱部と、該伝熱部よりも大きな径を有し、導電性を有する材料で形成した盤状の発熱部とで形成されていることを特徴とする請求項８に記載の単結晶の製造装置。The bottom-side heating member has a heat-transfer portion formed of a material having heat conductivity that transmits heat to a central portion of a bottom outer surface of the crucible, and a material having a larger diameter than the heat-transfer portion and having conductivity. The apparatus for producing a single crystal according to claim 8, wherein the apparatus is formed by a disk-shaped heat generating portion formed by: 前記底側加熱部材は、前記ルツボの底外面の中央部分に対応する位置に貫通穴を有する断熱性の材料で形成した断熱部材と、該断熱部材の貫通穴よりも大きな径を有し、導電性を有する材料で形成した盤状の発熱部とで形成されていることを特徴とする請求項８に記載の単結晶の製造装置。The bottom-side heating member has a heat-insulating member formed of a heat-insulating material having a through-hole at a position corresponding to a central portion of the bottom outer surface of the crucible, and has a diameter larger than the through-hole of the heat-insulating member, and 9. The apparatus for producing a single crystal according to claim 8, wherein the apparatus is formed by a disc-shaped heat generating portion formed of a material having property. 請求項１乃至１１のいずれか１項に記載の単結晶の製造装置または単結晶の製造方法により製造した単結晶。A single crystal manufactured by the single crystal manufacturing apparatus or the single crystal manufacturing method according to claim 1.
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